[BZ #12751]

* manual/memory.texi: Document MTASC-safety properties.

3 files changed, 539 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 0b7a976463..bcc89c4b3e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2014-01-31  Alexandre Oliva <aoliva@redhat.com>
 
+	[BZ #12751]
+	* manual/memory.texi: Document MTASC-safety properties.
+
+2014-01-31  Alexandre Oliva <aoliva@redhat.com>
+
 	* manual/math.texi: Document MTASC-safety properties.
 
 2014-01-31  Alexandre Oliva <aoliva@redhat.com>
diff --git a/NEWS b/NEWS
index 1d321b3726..7998c75eba 100644
--- a/NEWS
+++ b/NEWS
@@ -10,7 +10,7 @@ Version 2.19
 * The following bugs are resolved with this release:
 
   156, 387, 431, 762, 832, 926, 2801, 4772, 6786, 6787, 6807, 6810, 7003,
-  9721, 9954, 10253, 10278, 11087, 11157, 11214, 12100, 12486, 12986,
+  9721, 9954, 10253, 10278, 11087, 11157, 11214, 12100, 12486, 12751, 12986,
   13028, 13982, 13985, 14029, 14032, 14120, 14143, 14155, 14286, 14547,
   14699, 14752, 14782, 14876, 14910, 15004, 15048, 15073, 15089, 15128,
   15218, 15268, 15277, 15308, 15362, 15374, 15400, 15425, 15427, 15483,
diff --git a/manual/memory.texi b/manual/memory.texi
index 55a6a50ae6..4beb322c96 100644
--- a/manual/memory.texi
+++ b/manual/memory.texi
@@ -302,6 +302,245 @@ this function is in @file{stdlib.h}.
 @comment malloc.h stdlib.h
 @comment ISO
 @deftypefun {void *} malloc (size_t @var{size})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c Malloc hooks and __morecore pointers, as well as such parameters as
+@c max_n_mmaps and max_mmapped_mem, are accessed without guards, so they
+@c could pose a thread safety issue; in order to not declare malloc
+@c MT-unsafe, it's modifying the hooks and parameters while multiple
+@c threads are active that is regarded as unsafe.  An arena's next field
+@c is initialized and never changed again, except for main_arena's,
+@c that's protected by list_lock; next_free is only modified while
+@c list_lock is held too.  All other data members of an arena, as well
+@c as the metadata of the memory areas assigned to it, are only modified
+@c while holding the arena's mutex (fastbin pointers use catomic ops
+@c because they may be modified by free without taking the arena's
+@c lock).  Some reassurance was needed for fastbins, for it wasn't clear
+@c how they were initialized.  It turns out they are always
+@c zero-initialized: main_arena's, for being static data, and other
+@c arena's, for being just-mmapped memory.
+
+@c Leaking file descriptors and memory in case of cancellation is
+@c unavoidable without disabling cancellation, but the lock situation is
+@c a bit more complicated: we don't have fallback arenas for malloc to
+@c be safe to call from within signal handlers.  Error-checking mutexes
+@c or trylock could enable us to try and use alternate arenas, even with
+@c -DPER_THREAD (enabled by default), but supporting interruption
+@c (cancellation or signal handling) while holding the arena list mutex
+@c would require more work; maybe blocking signals and disabling async
+@c cancellation while manipulating the arena lists?
+
+@c __libc_malloc @asulock @aculock @acsfd @acsmem
+@c  force_reg ok
+@c  *malloc_hook unguarded
+@c  arena_lookup ok
+@c   tsd_getspecific ok, TLS
+@c  arena_lock @asulock @aculock @acsfd @acsmem
+@c   mutex_lock @asulock @aculock
+@c   arena_get2 @asulock @aculock @acsfd @acsmem
+@c    get_free_list @asulock @aculock
+@c     mutex_lock (list_lock) dup @asulock @aculock
+@c     mutex_unlock (list_lock) dup @aculock
+@c     mutex_lock (arena lock) dup @asulock @aculock [returns locked]
+@c     tsd_setspecific ok, TLS
+@c    __get_nprocs ext ok @acsfd
+@c    NARENAS_FROM_NCORES ok
+@c    catomic_compare_and_exchange_bool_acq ok
+@c    _int_new_arena ok @asulock @aculock @acsmem
+@c     new_heap ok @acsmem
+@c      mmap ok @acsmem
+@c      munmap ok @acsmem
+@c      mprotect ok
+@c     chunk2mem ok
+@c     set_head ok
+@c     tsd_setspecific dup ok
+@c     mutex_init ok
+@c     mutex_lock (just-created mutex) ok, returns locked
+@c     mutex_lock (list_lock) dup @asulock @aculock
+@c     atomic_write_barrier ok
+@c     mutex_unlock (list_lock) @aculock
+@c    catomic_decrement ok
+@c    reused_arena @asulock @aculock
+@c      reads&writes next_to_use and iterates over arena next without guards
+@c      those are harmless as long as we don't drop arenas from the
+@c      NEXT list, and we never do; when a thread terminates,
+@c      arena_thread_freeres prepends the arena to the free_list
+@c      NEXT_FREE list, but NEXT is never modified, so it's safe!
+@c     mutex_trylock (arena lock) @asulock @aculock
+@c     mutex_lock (arena lock) dup @asulock @aculock
+@c     tsd_setspecific dup ok
+@c  _int_malloc @acsfd @acsmem
+@c   checked_request2size ok
+@c    REQUEST_OUT_OF_RANGE ok
+@c    request2size ok
+@c   get_max_fast ok
+@c   fastbin_index ok
+@c   fastbin ok
+@c   catomic_compare_and_exhange_val_acq ok
+@c   malloc_printerr dup @mtsenv
+@c     if we get to it, we're toast already, undefined behavior must have
+@c     been invoked before
+@c    libc_message @mtsenv [no leaks with cancellation disabled]
+@c     FATAL_PREPARE ok
+@c      pthread_setcancelstate disable ok
+@c     libc_secure_getenv @mtsenv
+@c      getenv @mtsenv
+@c     open_not_cancel_2 dup @acsfd
+@c     strchrnul ok
+@c     WRITEV_FOR_FATAL ok
+@c      writev ok
+@c     mmap ok @acsmem
+@c     munmap ok @acsmem
+@c     BEFORE_ABORT @acsfd
+@c      backtrace ok
+@c      write_not_cancel dup ok
+@c      backtrace_symbols_fd @aculock
+@c      open_not_cancel_2 dup @acsfd
+@c      read_not_cancel dup ok
+@c      close_not_cancel_no_status dup @acsfd
+@c     abort ok
+@c    itoa_word ok
+@c    abort ok
+@c   check_remalloced_chunk ok/disabled
+@c   chunk2mem dup ok
+@c   alloc_perturb ok
+@c   in_smallbin_range ok
+@c   smallbin_index ok
+@c   bin_at ok
+@c   last ok
+@c   malloc_consolidate ok
+@c    get_max_fast dup ok
+@c    clear_fastchunks ok
+@c    unsorted_chunks dup ok
+@c    fastbin dup ok
+@c    atomic_exchange_acq ok
+@c    check_inuse_chunk dup ok/disabled
+@c    chunk_at_offset dup ok
+@c    chunksize dup ok
+@c    inuse_bit_at_offset dup ok
+@c    unlink dup ok
+@c    clear_inuse_bit_at_offset dup ok
+@c    in_smallbin_range dup ok
+@c    set_head dup ok
+@c    malloc_init_state ok
+@c     bin_at dup ok
+@c     set_noncontiguous dup ok
+@c     set_max_fast dup ok
+@c     initial_top ok
+@c      unsorted_chunks dup ok
+@c    check_malloc_state ok/disabled
+@c   set_inuse_bit_at_offset ok
+@c   check_malloced_chunk ok/disabled
+@c   largebin_index ok
+@c   have_fastchunks ok
+@c   unsorted_chunks ok
+@c    bin_at ok
+@c   chunksize ok
+@c   chunk_at_offset ok
+@c   set_head ok
+@c   set_foot ok
+@c   mark_bin ok
+@c    idx2bit ok
+@c   first ok
+@c   unlink ok
+@c    malloc_printerr dup ok
+@c    in_smallbin_range dup ok
+@c   idx2block ok
+@c   idx2bit dup ok
+@c   next_bin ok
+@c   sysmalloc @acsfd @acsmem
+@c    MMAP @acsmem
+@c    set_head dup ok
+@c    check_chunk ok/disabled
+@c    chunk2mem dup ok
+@c    chunksize dup ok
+@c    chunk_at_offset dup ok
+@c    heap_for_ptr ok
+@c    grow_heap ok
+@c     mprotect ok
+@c    set_head dup ok
+@c    new_heap @acsmem
+@c     MMAP dup @acsmem
+@c     munmap @acsmem
+@c    top ok
+@c    set_foot dup ok
+@c    contiguous ok
+@c    MORECORE ok
+@c     *__morecore ok unguarded
+@c      __default_morecore
+@c       sbrk ok
+@c    force_reg dup ok
+@c    *__after_morecore_hook unguarded
+@c    set_noncontiguous ok
+@c    malloc_printerr dup ok
+@c    _int_free (have_lock) @acsfd @acsmem [@asulock @aculock]
+@c     chunksize dup ok
+@c     mutex_unlock dup @aculock/!have_lock
+@c     malloc_printerr dup ok
+@c     check_inuse_chunk ok/disabled
+@c     chunk_at_offset dup ok
+@c     mutex_lock dup @asulock @aculock/@have_lock
+@c     chunk2mem dup ok
+@c     free_perturb ok
+@c     set_fastchunks ok
+@c      catomic_and ok
+@c     fastbin_index dup ok
+@c     fastbin dup ok
+@c     catomic_compare_and_exchange_val_rel ok
+@c     chunk_is_mmapped ok
+@c     contiguous dup ok
+@c     prev_inuse ok
+@c     unlink dup ok
+@c     inuse_bit_at_offset dup ok
+@c     clear_inuse_bit_at_offset ok
+@c     unsorted_chunks dup ok
+@c     in_smallbin_range dup ok
+@c     set_head dup ok
+@c     set_foot dup ok
+@c     check_free_chunk ok/disabled
+@c     check_chunk dup ok/disabled
+@c     have_fastchunks dup ok
+@c     malloc_consolidate dup ok
+@c     systrim ok
+@c      MORECORE dup ok
+@c      *__after_morecore_hook dup unguarded
+@c      set_head dup ok
+@c      check_malloc_state ok/disabled
+@c     top dup ok
+@c     heap_for_ptr dup ok
+@c     heap_trim @acsfd @acsmem
+@c      top dup ok
+@c      chunk_at_offset dup ok
+@c      prev_chunk ok
+@c      chunksize dup ok
+@c      prev_inuse dup ok
+@c      delete_heap @acsmem
+@c       munmap dup @acsmem
+@c      unlink dup ok
+@c      set_head dup ok
+@c      shrink_heap @acsfd
+@c       check_may_shrink_heap @acsfd
+@c        open_not_cancel_2 @acsfd
+@c        read_not_cancel ok
+@c        close_not_cancel_no_status @acsfd
+@c       MMAP dup ok
+@c       madvise ok
+@c     munmap_chunk @acsmem
+@c      chunksize dup ok
+@c      chunk_is_mmapped dup ok
+@c      chunk2mem dup ok
+@c      malloc_printerr dup ok
+@c      munmap dup @acsmem
+@c    check_malloc_state ok/disabled
+@c  arena_get_retry @asulock @aculock @acsfd @acsmem
+@c   mutex_unlock dup @aculock
+@c   mutex_lock dup @asulock @aculock
+@c   arena_get2 dup @asulock @aculock @acsfd @acsmem
+@c  mutex_unlock @aculock
+@c  mem2chunk ok
+@c  chunk_is_mmapped ok
+@c  arena_for_chunk ok
+@c   chunk_non_main_arena ok
+@c   heap_for_ptr ok
 This function returns a pointer to a newly allocated block @var{size}
 bytes long, or a null pointer if the block could not be allocated.
 @end deftypefun
@@ -407,6 +646,21 @@ The prototype for this function is in @file{stdlib.h}.
 @comment malloc.h stdlib.h
 @comment ISO
 @deftypefun void free (void *@var{ptr})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c __libc_free @asulock @aculock @acsfd @acsmem
+@c   releasing memory into fastbins modifies the arena without taking
+@c   its mutex, but catomic operations ensure safety.  If two (or more)
+@c   threads are running malloc and have their own arenas locked when
+@c   each gets a signal whose handler free()s large (non-fastbin-able)
+@c   blocks from each other's arena, we deadlock; this is a more general
+@c   case of @asulock.
+@c  *__free_hook unguarded
+@c  mem2chunk ok
+@c  chunk_is_mmapped ok, chunk bits not modified after allocation
+@c  chunksize ok
+@c  munmap_chunk dup @acsmem
+@c  arena_for_chunk dup ok
+@c  _int_free (!have_lock) dup @asulock @aculock @acsfd @acsmem
 The @code{free} function deallocates the block of memory pointed at
 by @var{ptr}.
 @end deftypefun
@@ -414,6 +668,8 @@ by @var{ptr}.
 @comment stdlib.h
 @comment Sun
 @deftypefun void cfree (void *@var{ptr})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c alias to free
 This function does the same thing as @code{free}.  It's provided for
 backward compatibility with SunOS; you should use @code{free} instead.
 @end deftypefun
@@ -471,6 +727,48 @@ is declared in @file{stdlib.h}.
 @comment malloc.h stdlib.h
 @comment ISO
 @deftypefun {void *} realloc (void *@var{ptr}, size_t @var{newsize})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c It may call the implementations of malloc and free, so all of their
+@c issues arise, plus the realloc hook, also accessed without guards.
+
+@c __libc_realloc @asulock @aculock @acsfd @acsmem
+@c  *__realloc_hook unguarded
+@c  __libc_free dup @asulock @aculock @acsfd @acsmem
+@c  __libc_malloc dup @asulock @aculock @acsfd @acsmem
+@c  mem2chunk dup ok
+@c  chunksize dup ok
+@c  malloc_printerr dup ok
+@c  checked_request2size dup ok
+@c  chunk_is_mmapped dup ok
+@c  mremap_chunk
+@c   chunksize dup ok
+@c   __mremap ok
+@c   set_head dup ok
+@c  MALLOC_COPY ok
+@c   memcpy ok
+@c  munmap_chunk dup @acsmem
+@c  arena_for_chunk dup ok
+@c  mutex_lock (arena mutex) dup @asulock @aculock
+@c  _int_realloc @acsfd @acsmem
+@c   malloc_printerr dup ok
+@c   check_inuse_chunk dup ok/disabled
+@c   chunk_at_offset dup ok
+@c   chunksize dup ok
+@c   set_head_size dup ok
+@c   chunk_at_offset dup ok
+@c   set_head dup ok
+@c   chunk2mem dup ok
+@c   inuse dup ok
+@c   unlink dup ok
+@c   _int_malloc dup @acsfd @acsmem
+@c   mem2chunk dup ok
+@c   MALLOC_COPY dup ok
+@c   _int_free (have_lock) dup @acsfd @acsmem
+@c   set_inuse_bit_at_offset dup ok
+@c   set_head dup ok
+@c  mutex_unlock (arena mutex) dup @aculock
+@c  _int_free (!have_lock) dup @asulock @aculock @acsfd @acsmem
+
 The @code{realloc} function changes the size of the block whose address is
 @var{ptr} to be @var{newsize}.
 
@@ -530,6 +828,25 @@ is declared in @file{stdlib.h}.
 @comment malloc.h stdlib.h
 @comment ISO
 @deftypefun {void *} calloc (size_t @var{count}, size_t @var{eltsize})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c Same caveats as malloc.
+
+@c __libc_calloc @asulock @aculock @acsfd @acsmem
+@c  *__malloc_hook dup unguarded
+@c  memset dup ok
+@c  arena_get @asulock @aculock @acsfd @acsmem
+@c   arena_lookup dup ok
+@c   arena_lock dup @asulock @aculock @acsfd @acsmem
+@c  top dup ok
+@c  chunksize dup ok
+@c  heap_for_ptr dup ok
+@c  _int_malloc dup @acsfd @acsmem
+@c  arena_get_retry dup @asulock @aculock @acsfd @acsmem
+@c  mutex_unlock dup @aculock
+@c  mem2chunk dup ok
+@c  chunk_is_mmapped dup ok
+@c  MALLOC_ZERO ok
+@c   memset dup ok
 This function allocates a block long enough to contain a vector of
 @var{count} elements, each of size @var{eltsize}.  Its contents are
 cleared to zero before @code{calloc} returns.
@@ -622,6 +939,8 @@ power of two than that, use @code{aligned_alloc} or @code{posix_memalign}.
 
 @comment stdlib.h
 @deftypefun {void *} aligned_alloc (size_t @var{alignment}, size_t @var{size})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c Alias to memalign.
 The @code{aligned_alloc} function allocates a block of @var{size} bytes whose
 address is a multiple of @var{alignment}.  The @var{alignment} must be a
 power of two and @var{size} must be a multiple of @var{alignment}.
@@ -645,6 +964,29 @@ portability to modern non-POSIX systems than @code{posix_memalign}.
 @comment malloc.h
 @comment BSD
 @deftypefun {void *} memalign (size_t @var{boundary}, size_t @var{size})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c Same issues as malloc.  The padding bytes are safely freed in
+@c _int_memalign, with the arena still locked.
+
+@c __libc_memalign @asulock @aculock @acsfd @acsmem
+@c  *__memalign_hook dup unguarded
+@c  __libc_malloc dup @asulock @aculock @acsfd @acsmem
+@c  arena_get dup @asulock @aculock @acsfd @acsmem
+@c  _int_memalign @acsfd @acsmem
+@c   _int_malloc dup @acsfd @acsmem
+@c   checked_request2size dup ok
+@c   mem2chunk dup ok
+@c   chunksize dup ok
+@c   chunk_is_mmapped dup ok
+@c   set_head dup ok
+@c   chunk2mem dup ok
+@c   set_inuse_bit_at_offset dup ok
+@c   set_head_size dup ok
+@c   _int_free (have_lock) dup @acsfd @acsmem
+@c   chunk_at_offset dup ok
+@c   check_inuse_chunk dup ok
+@c  arena_get_retry dup @asulock @aculock @acsfd @acsmem
+@c  mutex_unlock dup @aculock
 The @code{memalign} function allocates a block of @var{size} bytes whose
 address is a multiple of @var{boundary}.  The @var{boundary} must be a
 power of two!  The function @code{memalign} works by allocating a
@@ -670,6 +1012,10 @@ The @code{memalign} function is obsolete and @code{aligned_alloc} or
 @comment stdlib.h
 @comment POSIX
 @deftypefun int posix_memalign (void **@var{memptr}, size_t @var{alignment}, size_t @var{size})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c Calls memalign unless the requirements are not met (powerof2 macro is
+@c safe given an automatic variable as an argument) or there's a
+@c memalign hook (accessed unguarded, but safely).
 The @code{posix_memalign} function is similar to the @code{memalign}
 function in that it returns a buffer of @var{size} bytes aligned to a
 multiple of @var{alignment}.  But it adds one requirement to the
@@ -698,6 +1044,39 @@ systems that do not support @w{ISO C11}.
 @comment malloc.h stdlib.h
 @comment BSD
 @deftypefun {void *} valloc (size_t @var{size})
+@safety{@prelim{}@mtunsafe{@mtuinit{}}@asunsafe{@asuinit{} @asulock{}}@acunsafe{@acuinit{} @aculock{} @acsfd{} @acsmem{}}}
+@c __libc_valloc @mtuinit @asuinit @asulock @aculock @acsfd @acsmem
+@c  ptmalloc_init (once) @mtsenv @asulock @aculock @acsfd @acsmem
+@c   _dl_addr @asucorrupt? @aculock
+@c    __rtld_lock_lock_recursive (dl_load_lock) @asucorrupt? @aculock
+@c    _dl_find_dso_for_object ok, iterates over dl_ns and its _ns_loaded objs
+@c      the ok above assumes no partial updates on dl_ns and _ns_loaded
+@c      that could confuse a _dl_addr call in a signal handler
+@c     _dl_addr_inside_object ok
+@c    determine_info ok
+@c    __rtld_lock_unlock_recursive (dl_load_lock) @aculock
+@c   thread_atfork @asulock @aculock @acsfd @acsmem
+@c    __register_atfork @asulock @aculock @acsfd @acsmem
+@c     lll_lock (__fork_lock) @asulock @aculock
+@c     fork_handler_alloc @asulock @aculock @acsfd @acsmem
+@c      calloc dup @asulock @aculock @acsfd @acsmem
+@c     __linkin_atfork ok
+@c      catomic_compare_and_exchange_bool_acq ok
+@c     lll_unlock (__fork_lock) @aculock
+@c   *_environ @mtsenv
+@c   next_env_entry ok
+@c   strcspn dup ok
+@c   __libc_mallopt dup @mtasuconst:mallopt [setting mp_]
+@c   __malloc_check_init @mtasuconst:malloc_hooks [setting hooks]
+@c   *__malloc_initialize_hook unguarded, ok
+@c  *__memalign_hook dup ok, unguarded
+@c  arena_get dup @asulock @aculock @acsfd @acsmem
+@c  _int_valloc @acsfd @acsmem
+@c   malloc_consolidate dup ok
+@c   _int_memalign dup @acsfd @acsmem
+@c  arena_get_retry dup @asulock @aculock @acsfd @acsmem
+@c  _int_memalign dup @acsfd @acsmem
+@c  mutex_unlock dup @aculock
 Using @code{valloc} is like using @code{memalign} and passing the page size
 as the value of the second argument.  It is implemented like this:
 
@@ -725,6 +1104,14 @@ interface, defined in @file{malloc.h}.
 @pindex malloc.h
 
 @deftypefun int mallopt (int @var{param}, int @var{value})
+@safety{@prelim{}@mtunsafe{@mtuinit{} @mtasuconst{:mallopt}}@asunsafe{@asuinit{} @asulock{}}@acunsafe{@acuinit{} @aculock{}}}
+@c __libc_mallopt @mtuinit @mtasuconst:mallopt @asuinit @asulock @aculock
+@c  ptmalloc_init (once) dup @mtsenv @asulock @aculock @acsfd @acsmem
+@c  mutex_lock (main_arena->mutex) @asulock @aculock
+@c  malloc_consolidate dup ok
+@c  set_max_fast ok
+@c  mutex_unlock dup @aculock
+
 When calling @code{mallopt}, the @var{param} argument specifies the
 parameter to be set, and @var{value} the new value to be set.  Possible
 choices for @var{param}, as defined in @file{malloc.h}, are:
@@ -781,6 +1168,17 @@ declared in @file{mcheck.h}.
 @comment mcheck.h
 @comment GNU
 @deftypefun int mcheck (void (*@var{abortfn}) (enum mcheck_status @var{status}))
+@safety{@prelim{}@mtunsafe{@mtasurace{:mcheck} @mtasuconst{:malloc_hooks}}@asunsafe{@asucorrupt{}}@acunsafe{@acucorrupt{}}}
+@c The hooks must be set up before malloc is first used, which sort of
+@c implies @mtuinit/@asuinit but since the function is a no-op if malloc
+@c was already used, that doesn't pose any safety issues.  The actual
+@c problem is with the hooks, designed for single-threaded
+@c fully-synchronous operation: they manage an unguarded linked list of
+@c allocated blocks, and get temporarily overwritten before calling the
+@c allocation functions recursively while holding the old hooks.  There
+@c are no guards for thread safety, and inconsistent hooks may be found
+@c within signal handlers or left behind in case of cancellation.
+
 Calling @code{mcheck} tells @code{malloc} to perform occasional
 consistency checks.  These will catch things such as writing
 past the end of a block that was allocated with @code{malloc}.
@@ -823,6 +1221,18 @@ must be called before the first such function.
 @end deftypefun
 
 @deftypefun {enum mcheck_status} mprobe (void *@var{pointer})
+@safety{@prelim{}@mtunsafe{@mtasurace{:mcheck} @mtasuconst{:malloc_hooks}}@asunsafe{@asucorrupt{}}@acunsafe{@acucorrupt{}}}
+@c The linked list of headers may be modified concurrently by other
+@c threads, and it may find a partial update if called from a signal
+@c handler.  It's mostly read only, so cancelling it might be safe, but
+@c it will modify global state that, if cancellation hits at just the
+@c right spot, may be left behind inconsistent.  This path is only taken
+@c if checkhdr finds an inconsistency.  If the inconsistency could only
+@c occur because of earlier undefined behavior, that wouldn't be an
+@c additional safety issue problem, but because of the other concurrency
+@c issues in the mcheck hooks, the apparent inconsistency could be the
+@c result of mcheck's own internal data race.  So, AC-Unsafe it is.
+
 The @code{mprobe} function lets you explicitly check for inconsistencies
 in a particular allocated block.  You must have already called
 @code{mcheck} at the beginning of the program, to do its occasional
@@ -1137,6 +1547,24 @@ space's data segment).
 @comment malloc.h
 @comment SVID
 @deftypefun {struct mallinfo} mallinfo (void)
+@safety{@prelim{}@mtunsafe{@mtuinit{} @mtasuconst{:mallopt}}@asunsafe{@asuinit{} @asulock{}}@acunsafe{@acuinit{} @aculock{}}}
+@c Accessing mp_.n_mmaps and mp_.max_mmapped_mem, modified with atomics
+@c but non-atomically elsewhere, may get us inconsistent results.  We
+@c mark the statistics as unsafe, rather than the fast-path functions
+@c that collect the possibly inconsistent data.
+
+@c __libc_mallinfo @mtuinit @mtasuconst:mallopt @asuinit @asulock @aculock
+@c  ptmalloc_init (once) dup @mtsenv @asulock @aculock @acsfd @acsmem
+@c  mutex_lock dup @asulock @aculock
+@c  int_mallinfo @mtasuconst:mallopt [mp_ access on main_arena]
+@c   malloc_consolidate dup ok
+@c   check_malloc_state dup ok/disabled
+@c   chunksize dup ok
+@c   fastbin dupo ok
+@c   bin_at dup ok
+@c   last dup ok
+@c  mutex_unlock @aculock
+
 This function returns information about the current dynamic memory usage
 in a structure of type @code{struct mallinfo}.
 @end deftypefun
@@ -1235,6 +1663,20 @@ penalties for the program if the debugging mode is not enabled.
 @comment mcheck.h
 @comment GNU
 @deftypefun void mtrace (void)
+@safety{@prelim{}@mtunsafe{@mtsenv{} @mtasurace{:mtrace} @mtasuconst{:malloc_hooks} @mtuinit{}}@asunsafe{@asuinit{} @ascuheap{} @asucorrupt{} @asulock{}}@acunsafe{@acuinit{} @acucorrupt{} @aculock{} @acsfd{} @acsmem{}}}
+@c Like the mcheck hooks, these are not designed with thread safety in
+@c mind, because the hook pointers are temporarily modified without
+@c regard to other threads, signals or cancellation.
+
+@c mtrace @mtuinit @mtasurace:mtrace @mtsenv @asuinit @ascuheap @asucorrupt @acuinit @acucorrupt @aculock @acsfd @acsmem
+@c  __libc_secure_getenv dup @mtsenv
+@c  malloc dup @ascuheap @acsmem
+@c  fopen dup @ascuheap @asulock @aculock @acsmem @acsfd
+@c  fcntl dup ok
+@c  setvbuf dup @aculock
+@c  fprintf dup (on newly-created stream) @aculock
+@c  __cxa_atexit (once) dup @asulock @aculock @acsmem
+@c  free dup @ascuheap @acsmem
 When the @code{mtrace} function is called it looks for an environment
 variable named @code{MALLOC_TRACE}.  This variable is supposed to
 contain a valid file name.  The user must have write access.  If the
@@ -1258,6 +1700,11 @@ systems.  The prototype can be found in @file{mcheck.h}.
 @comment mcheck.h
 @comment GNU
 @deftypefun void muntrace (void)
+@safety{@prelim{}@mtunsafe{@mtasurace{:mtrace} @mtasuconst{:malloc_hooks} @mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @acsmem{} @aculock{} @acsfd{}}}
+
+@c muntrace @mtasurace:mtrace @mtslocale @asucorrupt @ascuheap @acucorrupt @acsmem @aculock @acsfd
+@c  fprintf (fputs) dup @mtslocale @asucorrupt @ascuheap @acsmem @aculock @acucorrupt
+@c  fclose dup @ascuheap @asulock @aculock @acsmem @acsfd
 The @code{muntrace} function can be called after @code{mtrace} was used
 to enable tracing the @code{malloc} calls.  If no (successful) call of
 @code{mtrace} was made @code{muntrace} does nothing.
@@ -1569,6 +2016,20 @@ as an obstack, it must initialize the obstack by calling
 @comment obstack.h
 @comment GNU
 @deftypefun int obstack_init (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{@acsmem{}}}
+@c obstack_init @mtsrace:obstack-ptr @acsmem
+@c  _obstack_begin @acsmem
+@c    chunkfun = obstack_chunk_alloc (suggested malloc)
+@c    freefun = obstack_chunk_free (suggested free)
+@c   *chunkfun @acsmem
+@c    obstack_chunk_alloc user-supplied
+@c   *obstack_alloc_failed_handler user-supplied
+@c    -> print_and_abort (default)
+@c
+@c print_and_abort
+@c  _ dup @ascuintl
+@c  fxprintf dup @asucorrupt @aculock @acucorrupt
+@c  exit @acucorrupt?
 Initialize obstack @var{obstack-ptr} for allocation of objects.  This
 function calls the obstack's @code{obstack_chunk_alloc} function.  If
 allocation of memory fails, the function pointed to by
@@ -1624,6 +2085,10 @@ The most direct way to allocate an object in an obstack is with
 @comment obstack.h
 @comment GNU
 @deftypefun {void *} obstack_alloc (struct obstack *@var{obstack-ptr}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_alloc @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  obstack_blank dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  obstack_finish dup @mtsrace:obstack-ptr @acucorrupt
 This allocates an uninitialized block of @var{size} bytes in an obstack
 and returns its address.  Here @var{obstack-ptr} specifies which obstack
 to allocate the block in; it is the address of the @code{struct obstack}
@@ -1658,6 +2123,10 @@ To allocate a block with specified contents, use the function
 @comment obstack.h
 @comment GNU
 @deftypefun {void *} obstack_copy (struct obstack *@var{obstack-ptr}, void *@var{address}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_copy @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  obstack_grow dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  obstack_finish dup @mtsrace:obstack-ptr @acucorrupt
 This allocates a block and initializes it by copying @var{size}
 bytes of data starting at @var{address}.  It calls
 @code{obstack_alloc_failed_handler} if allocation of memory by
@@ -1667,6 +2136,10 @@ bytes of data starting at @var{address}.  It calls
 @comment obstack.h
 @comment GNU
 @deftypefun {void *} obstack_copy0 (struct obstack *@var{obstack-ptr}, void *@var{address}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_copy0 @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  obstack_grow0 dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  obstack_finish dup @mtsrace:obstack-ptr @acucorrupt
 Like @code{obstack_copy}, but appends an extra byte containing a null
 character.  This extra byte is not counted in the argument @var{size}.
 @end deftypefun
@@ -1699,6 +2172,10 @@ in the same obstack.
 @comment obstack.h
 @comment GNU
 @deftypefun void obstack_free (struct obstack *@var{obstack-ptr}, void *@var{object})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{}}}
+@c obstack_free @mtsrace:obstack-ptr @acucorrupt
+@c  (obstack_free) @mtsrace:obstack-ptr @acucorrupt
+@c   *freefun dup user-supplied
 If @var{object} is a null pointer, everything allocated in the obstack
 is freed.  Otherwise, @var{object} must be the address of an object
 allocated in the obstack.  Then @var{object} is freed, along with
@@ -1803,6 +2280,13 @@ already added to the growing object will become part of the other object.
 @comment obstack.h
 @comment GNU
 @deftypefun void obstack_blank (struct obstack *@var{obstack-ptr}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_blank @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  _obstack_newchunk @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c   *chunkfun dup @acsmem
+@c   *obstack_alloc_failed_handler dup user-supplied
+@c   *freefun
+@c  obstack_blank_fast dup @mtsrace:obstack-ptr
 The most basic function for adding to a growing object is
 @code{obstack_blank}, which adds space without initializing it.
 @end deftypefun
@@ -1810,6 +2294,10 @@ The most basic function for adding to a growing object is
 @comment obstack.h
 @comment GNU
 @deftypefun void obstack_grow (struct obstack *@var{obstack-ptr}, void *@var{data}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_grow @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  _obstack_newchunk dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  memcpy ok
 To add a block of initialized space, use @code{obstack_grow}, which is
 the growing-object analogue of @code{obstack_copy}.  It adds @var{size}
 bytes of data to the growing object, copying the contents from
@@ -1819,6 +2307,12 @@ bytes of data to the growing object, copying the contents from
 @comment obstack.h
 @comment GNU
 @deftypefun void obstack_grow0 (struct obstack *@var{obstack-ptr}, void *@var{data}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_grow0 @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c   (no sequence point between storing NUL and incrementing next_free)
+@c   (multiple changes to next_free => @acucorrupt)
+@c  _obstack_newchunk dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  memcpy ok
 This is the growing-object analogue of @code{obstack_copy0}.  It adds
 @var{size} bytes copied from @var{data}, followed by an additional null
 character.
@@ -1827,6 +2321,10 @@ character.
 @comment obstack.h
 @comment GNU
 @deftypefun void obstack_1grow (struct obstack *@var{obstack-ptr}, char @var{c})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_1grow @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  _obstack_newchunk dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  obstack_1grow_fast dup @mtsrace:obstack-ptr @acucorrupt @acsmem
 To add one character at a time, use the function @code{obstack_1grow}.
 It adds a single byte containing @var{c} to the growing object.
 @end deftypefun
@@ -1834,6 +2332,10 @@ It adds a single byte containing @var{c} to the growing object.
 @comment obstack.h
 @comment GNU
 @deftypefun void obstack_ptr_grow (struct obstack *@var{obstack-ptr}, void *@var{data})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_ptr_grow @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  _obstack_newchunk dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  obstack_ptr_grow_fast dup @mtsrace:obstack-ptr
 Adding the value of a pointer one can use the function
 @code{obstack_ptr_grow}.  It adds @code{sizeof (void *)} bytes
 containing the value of @var{data}.
@@ -1842,6 +2344,10 @@ containing the value of @var{data}.
 @comment obstack.h
 @comment GNU
 @deftypefun void obstack_int_grow (struct obstack *@var{obstack-ptr}, int @var{data})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_int_grow @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  _obstack_newchunk dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c  obstack_int_grow_fast dup @mtsrace:obstack-ptr
 A single value of type @code{int} can be added by using the
 @code{obstack_int_grow} function.  It adds @code{sizeof (int)} bytes to
 the growing object and initializes them with the value of @var{data}.
@@ -1850,6 +2356,8 @@ the growing object and initializes them with the value of @var{data}.
 @comment obstack.h
 @comment GNU
 @deftypefun {void *} obstack_finish (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{}}}
+@c obstack_finish @mtsrace:obstack-ptr @acucorrupt
 When you are finished growing the object, use the function
 @code{obstack_finish} to close it off and return its final address.
 
@@ -1869,6 +2377,7 @@ declared as follows:
 @comment obstack.h
 @comment GNU
 @deftypefun int obstack_object_size (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
 This function returns the current size of the growing object, in bytes.
 Remember to call this function @emph{before} finishing the object.
 After it is finished, @code{obstack_object_size} will return zero.
@@ -1912,6 +2421,7 @@ in the current chunk.  It is declared as follows:
 @comment obstack.h
 @comment GNU
 @deftypefun int obstack_room (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
 This returns the number of bytes that can be added safely to the current
 growing object (or to an object about to be started) in obstack
 @var{obstack} using the fast growth functions.
@@ -1923,6 +2433,9 @@ for adding data to a growing object:
 @comment obstack.h
 @comment GNU
 @deftypefun void obstack_1grow_fast (struct obstack *@var{obstack-ptr}, char @var{c})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_1grow_fast @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c   (no sequence point between copying c and incrementing next_free)
 The function @code{obstack_1grow_fast} adds one byte containing the
 character @var{c} to the growing object in obstack @var{obstack-ptr}.
 @end deftypefun
@@ -1930,6 +2443,8 @@ character @var{c} to the growing object in obstack @var{obstack-ptr}.
 @comment obstack.h
 @comment GNU
 @deftypefun void obstack_ptr_grow_fast (struct obstack *@var{obstack-ptr}, void *@var{data})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
+@c obstack_ptr_grow_fast @mtsrace:obstack-ptr
 The function @code{obstack_ptr_grow_fast} adds @code{sizeof (void *)}
 bytes containing the value of @var{data} to the growing object in
 obstack @var{obstack-ptr}.
@@ -1938,6 +2453,8 @@ obstack @var{obstack-ptr}.
 @comment obstack.h
 @comment GNU
 @deftypefun void obstack_int_grow_fast (struct obstack *@var{obstack-ptr}, int @var{data})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
+@c obstack_int_grow_fast @mtsrace:obstack-ptr
 The function @code{obstack_int_grow_fast} adds @code{sizeof (int)} bytes
 containing the value of @var{data} to the growing object in obstack
 @var{obstack-ptr}.
@@ -1946,6 +2463,8 @@ containing the value of @var{data} to the growing object in obstack
 @comment obstack.h
 @comment GNU
 @deftypefun void obstack_blank_fast (struct obstack *@var{obstack-ptr}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
+@c obstack_blank_fast @mtsrace:obstack-ptr
 The function @code{obstack_blank_fast} adds @var{size} bytes to the
 growing object in obstack @var{obstack-ptr} without initializing them.
 @end deftypefun
@@ -2004,6 +2523,7 @@ still growing it.
 @comment obstack.h
 @comment GNU
 @deftypefun {void *} obstack_base (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asucorrupt{}}@acsafe{}}
 This function returns the tentative address of the beginning of the
 currently growing object in @var{obstack-ptr}.  If you finish the object
 immediately, it will have that address.  If you make it larger first, it
@@ -2017,6 +2537,7 @@ chunk).
 @comment obstack.h
 @comment GNU
 @deftypefun {void *} obstack_next_free (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asucorrupt{}}@acsafe{}}
 This function returns the address of the first free byte in the current
 chunk of obstack @var{obstack-ptr}.  This is the end of the currently
 growing object.  If no object is growing, @code{obstack_next_free}
@@ -2026,6 +2547,8 @@ returns the same value as @code{obstack_base}.
 @comment obstack.h
 @comment GNU
 @deftypefun int obstack_object_size (struct obstack *@var{obstack-ptr})
+@c dup
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
 This function returns the size in bytes of the currently growing object.
 This is equivalent to
 
@@ -2050,6 +2573,7 @@ this:
 @comment obstack.h
 @comment GNU
 @deftypefn Macro int obstack_alignment_mask (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 The value is a bit mask; a bit that is 1 indicates that the corresponding
 bit in the address of an object should be 0.  The mask value should be one
 less than a power of 2; the effect is that all object addresses are
@@ -2117,6 +2641,7 @@ not to waste too much memory in the portion of the last chunk not yet used.
 @comment obstack.h
 @comment GNU
 @deftypefn Macro int obstack_chunk_size (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 This returns the chunk size of the given obstack.
 @end deftypefn
 
@@ -2236,6 +2761,7 @@ a BSD extension.
 @comment stdlib.h
 @comment GNU, BSD
 @deftypefun {void *} alloca (size_t @var{size})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 The return value of @code{alloca} is the address of a block of @var{size}
 bytes of memory, allocated in the stack frame of the calling function.
 @end deftypefun
@@ -2418,6 +2944,7 @@ system calls.
 @comment unistd.h
 @comment BSD
 @deftypefun int brk (void *@var{addr})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 
 @code{brk} sets the high end of the calling process' data segment to
 @var{addr}.
@@ -2460,6 +2987,8 @@ exceed the process' data storage limit.
 @comment unistd.h
 @comment BSD
 @deftypefun void *sbrk (ptrdiff_t @var{delta})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+
 This function is the same as @code{brk} except that you specify the new
 end of the data segment as an offset @var{delta} from the current end
 and on success the return value is the address of the resulting end of
@@ -2599,6 +3128,7 @@ this requirement.
 @comment sys/mman.h
 @comment POSIX.1b
 @deftypefun int mlock (const void *@var{addr}, size_t @var{len})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 
 @code{mlock} locks a range of the calling process' virtual pages.
 
@@ -2652,6 +3182,7 @@ wouldn't know what address to tell @code{mlock}.
 @comment sys/mman.h
 @comment POSIX.1b
 @deftypefun int munlock (const void *@var{addr}, size_t @var{len})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 
 @code{munlock} unlocks a range of the calling process' virtual pages.
 
@@ -2664,6 +3195,7 @@ failure.
 @comment sys/mman.h
 @comment POSIX.1b
 @deftypefun int mlockall (int @var{flags})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 
 @code{mlockall} locks all the pages in a process' virtual memory address
 space, and/or any that are added to it in the future.  This includes the
@@ -2740,6 +3272,7 @@ with @code{munlockall} and @code{munlock}.
 @comment sys/mman.h
 @comment POSIX.1b
 @deftypefun int munlockall (void)
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 
 @code{munlockall} unlocks every page in the calling process' virtual
 address space and turn off @code{MCL_FUTURE} future locking mode.