Add pretty printers for the NPTL lock types

This patch adds pretty printers for the following NPTL types:

- pthread_mutex_t
- pthread_mutexattr_t
- pthread_cond_t
- pthread_condattr_t
- pthread_rwlock_t
- pthread_rwlockattr_t

To load the pretty printers into your gdb session, do the following:

python
import sys
sys.path.insert(0, '/path/to/glibc/build/nptl/pretty-printers')
end

source /path/to/glibc/source/pretty-printers/nptl-printers.py

You can check which printers are registered and enabled by issuing the
'info pretty-printer' gdb command. Printers should trigger automatically when
trying to print a variable of one of the types mentioned above.

The printers are architecture-independent, and were tested on an AMD64 running
Ubuntu 14.04 and an x86 VM running Fedora 24.

In order to work, the printers need to know the values of various flags that
are scattered throughout pthread.h and pthreadP.h as enums and #defines. Since
replicating these constants in the printers file itself would create a
maintenance burden, I wrote a script called gen-py-const.awk that Makerules uses
to extract the constants. This script is pretty much the same as gen-as-const.awk,
except it doesn't cast the constant values to 'long' and is thorougly documented.
The constants need only to be enumerated in a .pysym file, which is then referenced
by a Make variable called gen-py-const-headers.

As for the install directory, I discussed this with Mike Frysinger and Siddhesh
Poyarekar, and we agreed that it can be handled in a separate patch, and shouldn't
block merging of this one.

In addition, I've written a series of test cases for the pretty printers.
Each lock type (mutex, condvar and rwlock) has two test programs, one for itself
and other for its related 'attributes' object. Each test program in turn has a
PExpect-based Python script that drives gdb and compares its output to the
expected printer's. The tests run on the glibc host, which is assumed to have
both gdb and PExpect; if either is absent the tests will fail with code 77
(UNSUPPORTED). For cross-testing you should use cross-test-ssh.sh as test-wrapper.
I've tested the printers on both native builds and a cross build using a Beaglebone
Black running Debian, with the build system's filesystem shared with the board
through NFS.

Finally, I've written a README that explains all this and more.

	* INSTALL: Regenerated.
	* Makeconfig: Add comments and whitespace to make the control flow
	clearer.
	(+link-printers-tests, +link-pie-printers-tests, CFLAGS-printers-tests,
	installed-rtld-LDFLAGS, built-rtld-LDFLAGS, link-libc-rpath,
	link-libc-tests-after-rpath-link, link-libc-printers-tests): New.
	(rtld-LDFLAGS, rtld-tests-LDFLAGS, link-libc-tests-rpath-link,
	link-libc-tests): Use the new variables as required.
	* Makerules ($(py-const)): New rule.
	generated: Add $(py-const).
	* README.pretty-printers: New file.
	* Rules (tests-printers-programs, tests-printers-out, py-env): New.
	(others): Depend on $(py-const).
	(tests): Depend on $(tests-printers-programs) or $(tests-printers-out),
	as required.  Pass $(tests-printers) to merge-test-results.sh.
	* manual/install.texi: Add requirements for testing the pretty printers.
	* nptl/Makefile (gen-py-const-headers, pretty-printers, tests-printers,
	CFLAGS-test-mutexattr-printers.c CFLAGS-test-mutex-printers.c,
	CFLAGS-test-condattr-printers.c, CFLAGS-test-cond-printers.c,
	CFLAGS-test-rwlockattr-printers.c CFLAGS-test-rwlock-printers.c,
	tests-printers-libs): Define.
	* nptl/nptl-printers.py: New file.
	* nptl/nptl_lock_constants.pysym: Likewise.
	* nptl/test-cond-printers.c: Likewise.
	* nptl/test-cond-printers.py: Likewise.
	* nptl/test-condattr-printers.c: Likewise.
	* nptl/test-condattr-printers.py: Likewise.
	* nptl/test-mutex-printers.c: Likewise.
	* nptl/test-mutex-printers.py: Likewise.
	* nptl/test-mutexattr-printers.c: Likewise.
	* nptl/test-mutexattr-printers.py: Likewise.
	* nptl/test-rwlock-printers.c: Likewise.
	* nptl/test-rwlock-printers.py: Likewise.
	* nptl/test-rwlockattr-printers.c: Likewise.
	* nptl/test-rwlockattr-printers.py: Likewise.
	* scripts/gen-py-const.awk: Likewise.
	* scripts/test_printers_common.py: Likewise.
	* scripts/test_printers_exceptions.py: Likewise.

1 files changed, 59 insertions, 17 deletions

diff --git a/Makeconfig b/Makeconfig
index a7858607b0..e9d8da9d60 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -416,6 +416,11 @@ $(+link-pie-before-libc) $(rtld-tests-LDFLAGS) $(link-libc-tests) \
 			 $(+link-pie-after-libc)
 $(call after-link,$@)
 endef
+define +link-pie-printers-tests
+$(+link-pie-before-libc) $(built-rtld-LDFLAGS) $(link-libc-printers-tests) \
+			 $(+link-pie-after-libc)
+$(call after-link,$@)
+endef
 endif
 # Command for statically linking programs with the C library.
 ifndef +link-static
@@ -445,7 +450,8 @@ ifeq (yes,$(build-pie-default))
 no-pie-ldflag = -no-pie
 +link = $(+link-pie)
 +link-tests = $(+link-pie-tests)
-else
++link-printers-tests = $(+link-pie-printers-tests)
+else  # not build-pie-default
 +link-before-libc = $(CC) -nostdlib -nostartfiles -o $@ \
 	      $(sysdep-LDFLAGS) $(LDFLAGS) $(LDFLAGS-$(@F)) \
 	      $(combreloc-LDFLAGS) $(relro-LDFLAGS) $(hashstyle-LDFLAGS) \
@@ -466,51 +472,87 @@ $(+link-before-libc) $(rtld-tests-LDFLAGS) $(link-libc-tests) \
 		     $(+link-after-libc)
 $(call after-link,$@)
 endef
-endif
-else
+define +link-printers-tests
+$(+link-before-libc) $(built-rtld-LDFLAGS) $(link-libc-printers-tests) \
+		     $(+link-after-libc)
+$(call after-link,$@)
+endef
+endif  # build-pie-default
+else  # build-static
 +link = $(+link-static)
 +link-tests = $(+link-static-tests)
-endif
-endif
++link-printers-tests = $(+link-static-tests)
+endif  # build-shared
+endif  # +link
+
+# The pretty printer test programs need to be compiled without optimizations
+# so they won't confuse gdb.  We could use either the 'GCC optimize' pragma
+# or the 'optimize' function attribute to achieve this; however, at least on
+# ARM, gcc always produces different debugging symbols when invoked with
+# a -O greater than 0 than when invoked with -O0, regardless of anything else
+# we're using to suppress optimizations.  Therefore, we need to explicitly pass
+# -O0 to it through CFLAGS.
+# Additionally, the build system will try to -include $(common-objpfx)/config.h
+# when compiling the tests, which will throw an error if some special macros
+# (such as __OPTIMIZE__ and IS_IN_build) aren't defined.  To avoid this, we
+# tell gcc to define IS_IN_build.
+CFLAGS-printers-tests := -O0 -ggdb3 -DIS_IN_build
+
 ifeq (yes,$(build-shared))
+# These indicate whether to link using the built ld.so or the installed one.
+installed-rtld-LDFLAGS = -Wl,-dynamic-linker=$(rtlddir)/$(rtld-installed-name)
+built-rtld-LDFLAGS = -Wl,-dynamic-linker=$(elf-objpfx)ld.so
+
 ifndef rtld-LDFLAGS
-rtld-LDFLAGS = -Wl,-dynamic-linker=$(rtlddir)/$(rtld-installed-name)
+rtld-LDFLAGS = $(installed-rtld-LDFLAGS)
 endif
+
 ifndef rtld-tests-LDFLAGS
 ifeq (yes,$(build-hardcoded-path-in-tests))
-rtld-tests-LDFLAGS = -Wl,-dynamic-linker=$(elf-objpfx)ld.so
+rtld-tests-LDFLAGS = $(built-rtld-LDFLAGS)
 else
-rtld-tests-LDFLAGS = $(rtld-LDFLAGS)
-endif
-endif
-endif
+rtld-tests-LDFLAGS = $(installed-rtld-LDFLAGS)
+endif  # build-hardcoded-path-in-tests
+endif  # rtld-tests-LDFLAGS
+
+endif  # build-shared
+
 ifndef link-libc
 ifeq (yes,$(build-shared))
 # We need the versioned name of libc.so in the deps of $(others) et al
 # so that the symlink to libc.so is created before anything tries to
 # run the linked programs.
+link-libc-rpath = -Wl,-rpath=$(rpath-link)
 link-libc-rpath-link = -Wl,-rpath-link=$(rpath-link)
+
 ifeq (yes,$(build-hardcoded-path-in-tests))
-link-libc-tests-rpath-link = -Wl,-rpath=$(rpath-link)
+link-libc-tests-rpath-link = $(link-libc-rpath)
 else
 link-libc-tests-rpath-link = $(link-libc-rpath-link)
-endif
+endif  # build-hardcoded-path-in-tests
+
 link-libc-before-gnulib = $(common-objpfx)libc.so$(libc.so-version) \
 			  $(common-objpfx)$(patsubst %,$(libtype.oS),c) \
 			  $(as-needed) $(elf-objpfx)ld.so \
 			  $(no-as-needed)
 link-libc = $(link-libc-rpath-link) $(link-libc-before-gnulib) $(gnulib)
+
+link-libc-tests-after-rpath-link = $(link-libc-before-gnulib) $(gnulib-tests)
 link-libc-tests = $(link-libc-tests-rpath-link) \
-		  $(link-libc-before-gnulib) $(gnulib-tests)
+		  $(link-libc-tests-after-rpath-link)
+# Pretty printer test programs always require rpath instead of rpath-link.
+link-libc-printers-tests = $(link-libc-rpath) \
+			   $(link-libc-tests-after-rpath-link)
+
 # This is how to find at build-time things that will be installed there.
 rpath-dirs = math elf dlfcn nss nis rt resolv crypt mathvec
 rpath-link = \
 $(common-objdir):$(subst $(empty) ,:,$(patsubst ../$(subdir),.,$(rpath-dirs:%=$(common-objpfx)%)))
-else
+else  # build-static
 link-libc = $(common-objpfx)libc.a $(otherlibs) $(gnulib) $(common-objpfx)libc.a $(gnulib)
 link-libc-tests = $(common-objpfx)libc.a $(otherlibs) $(gnulib-tests) $(common-objpfx)libc.a $(gnulib-tests)
-endif
-endif
+endif  # build-shared
+endif  # link-libc
 
 # Differences in the linkers on the various platforms.
 LDFLAGS-rpath-ORIGIN = -Wl,-rpath,'$$ORIGIN'