Add and move fall-through comments in system-specific code.

This patch fixes -Wimplicit-fallthrough warnings in system-specific
code that show up building glibc with -Wextra, by adding fall-through
comments, or moving existing such comments to the place required for
them to work (immediately before the case label being fallen through).

Tested with build-many-glibcs.py.

	* sysdeps/i386/dl-machine.h (elf_machine_rela): Add fall-through
	comments.
	* sysdeps/m68k/m680x0/fpu/s_cexp_template.c (s(__cexp)): Likewise.
	* sysdeps/m68k/memcopy.h (WORD_COPY_FWD): Likewise.
	(WORD_COPY_BWD): Likewise.
	* sysdeps/mach/hurd/ioctl.c (__ioctl): Likewise.
	* sysdeps/powerpc/powerpc64/dl-machine.h (elf_machine_rela):
	Likewise.
	* sysdeps/s390/iso-8859-1_cp037_z900.c (TR_LOOP): Likewise.
	* sysdeps/mips/dl-machine.h (elf_machine_reloc): Move fall-through
	comment.
	* sysdeps/mips/dl-trampoline.c (__dl_runtime_resolve): Likewise.

9 files changed, 46 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 08c2dc6d0d..2f1cfdfb5d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+2019-02-26  Joseph Myers  <joseph@codesourcery.com>
+
+	* sysdeps/i386/dl-machine.h (elf_machine_rela): Add fall-through
+	comments.
+	* sysdeps/m68k/m680x0/fpu/s_cexp_template.c (s(__cexp)): Likewise.
+	* sysdeps/m68k/memcopy.h (WORD_COPY_FWD): Likewise.
+	(WORD_COPY_BWD): Likewise.
+	* sysdeps/mach/hurd/ioctl.c (__ioctl): Likewise.
+	* sysdeps/powerpc/powerpc64/dl-machine.h (elf_machine_rela):
+	Likewise.
+	* sysdeps/s390/iso-8859-1_cp037_z900.c (TR_LOOP): Likewise.
+	* sysdeps/mips/dl-machine.h (elf_machine_reloc): Move fall-through
+	comment.
+	* sysdeps/mips/dl-trampoline.c (__dl_runtime_resolve): Likewise.
+
 2019-02-25  Joseph Myers  <joseph@codesourcery.com>
 
 	* dirent/dirent.h [!_DIRENT_HAVE_D_NAMLEN
diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
index 13cb03a7ab..1566d1282a 100644
--- a/sysdeps/i386/dl-machine.h
+++ b/sysdeps/i386/dl-machine.h
@@ -522,6 +522,7 @@ elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 	case R_386_SIZE32:
 	  /* Set to symbol size plus addend.  */
 	  value = sym->st_size;
+	  /* Fall through.  */
 	case R_386_GLOB_DAT:
 	case R_386_JMP_SLOT:
 	case R_386_32:
diff --git a/sysdeps/m68k/m680x0/fpu/s_cexp_template.c b/sysdeps/m68k/m680x0/fpu/s_cexp_template.c
index d214f5925b..13befb2d29 100644
--- a/sysdeps/m68k/m680x0/fpu/s_cexp_template.c
+++ b/sysdeps/m68k/m680x0/fpu/s_cexp_template.c
@@ -93,6 +93,7 @@ s(__cexp) (CFLOAT x)
 	      break;
 	    case 2:
 	      __real__ retval = -__real__ retval;
+	      /* Fall through.  */
 	    case 3:
 	      __imag__ retval = -__imag__ retval;
 	      break;
diff --git a/sysdeps/m68k/memcopy.h b/sysdeps/m68k/memcopy.h
index 66c39649da..aa4a1ab651 100644
--- a/sysdeps/m68k/memcopy.h
+++ b/sysdeps/m68k/memcopy.h
@@ -39,20 +39,28 @@
 	do								      \
 	  {								      \
 	    ((op_t *) dst_bp)[0] = ((op_t *) src_bp)[0];		      \
+	    /* Fall through.  */					      \
 	  case 7:							      \
 	    ((op_t *) dst_bp)[1] = ((op_t *) src_bp)[1];		      \
+	    /* Fall through.  */					      \
 	  case 6:							      \
 	    ((op_t *) dst_bp)[2] = ((op_t *) src_bp)[2];		      \
+	    /* Fall through.  */					      \
 	  case 5:							      \
 	    ((op_t *) dst_bp)[3] = ((op_t *) src_bp)[3];		      \
+	    /* Fall through.  */					      \
 	  case 4:							      \
 	    ((op_t *) dst_bp)[4] = ((op_t *) src_bp)[4];		      \
+	    /* Fall through.  */					      \
 	  case 3:							      \
 	    ((op_t *) dst_bp)[5] = ((op_t *) src_bp)[5];		      \
+	    /* Fall through.  */					      \
 	  case 2:							      \
 	    ((op_t *) dst_bp)[6] = ((op_t *) src_bp)[6];		      \
+	    /* Fall through.  */					      \
 	  case 1:							      \
 	    ((op_t *) dst_bp)[7] = ((op_t *) src_bp)[7];		      \
+	    /* Fall through.  */					      \
 	  case 0:							      \
 	    src_bp += 32;						      \
 	    dst_bp += 32;						      \
@@ -73,20 +81,28 @@
 	do								      \
 	  {								      \
 	    *--__dst_ep = *--__src_ep;					      \
+	    /* Fall through.  */					      \
 	  case 7:							      \
 	    *--__dst_ep = *--__src_ep;					      \
+	    /* Fall through.  */					      \
 	  case 6:							      \
 	    *--__dst_ep = *--__src_ep;					      \
+	    /* Fall through.  */					      \
 	  case 5:							      \
 	    *--__dst_ep = *--__src_ep;					      \
+	    /* Fall through.  */					      \
 	  case 4:							      \
 	    *--__dst_ep = *--__src_ep;					      \
+	    /* Fall through.  */					      \
 	  case 3:							      \
 	    *--__dst_ep = *--__src_ep;					      \
+	    /* Fall through.  */					      \
 	  case 2:							      \
 	    *--__dst_ep = *--__src_ep;					      \
+	    /* Fall through.  */					      \
 	  case 1:							      \
 	    *--__dst_ep = *--__src_ep;					      \
+	    /* Fall through.  */					      \
 	  case 0:							      \
 	    __nblocks--;						      \
 	  }								      \
diff --git a/sysdeps/mach/hurd/ioctl.c b/sysdeps/mach/hurd/ioctl.c
index cd630e179e..abd13f6bf7 100644
--- a/sysdeps/mach/hurd/ioctl.c
+++ b/sysdeps/mach/hurd/ioctl.c
@@ -177,6 +177,7 @@ __ioctl (int fd, unsigned long int request, ...)
 	case MACH_SEND_INVALID_REPLY:
 	case MACH_RCV_INVALID_NAME:
 	  __mig_dealloc_reply_port (m->msgh_local_port);
+	  /* Fall through.  */
 	default:
 	  return err;
 	}
@@ -318,6 +319,7 @@ __ioctl (int fd, unsigned long int request, ...)
     case EOPNOTSUPP:
       /* The server didn't understand the RPC.  */
       err = ENOTTY;
+      /* Fall through.  */
     default:
       return __hurd_fail (err);
     }
diff --git a/sysdeps/mips/dl-machine.h b/sysdeps/mips/dl-machine.h
index e82891fa3f..f9e7e90b41 100644
--- a/sysdeps/mips/dl-machine.h
+++ b/sysdeps/mips/dl-machine.h
@@ -712,8 +712,8 @@ elf_machine_reloc (struct link_map *map, ElfW(Addr) r_info,
 	 it's totally unnecessary.  */
       if (ELFW(R_SYM) (r_info) == 0)
 	break;
-      /* Fall through.  */
 #endif
+      /* Fall through.  */
     default:
       _dl_reloc_bad_type (map, r_type, 0);
       break;
diff --git a/sysdeps/mips/dl-trampoline.c b/sysdeps/mips/dl-trampoline.c
index 568c8a10ce..5a8cc7dc56 100644
--- a/sysdeps/mips/dl-trampoline.c
+++ b/sysdeps/mips/dl-trampoline.c
@@ -166,8 +166,8 @@ __dl_runtime_resolve (ElfW(Word) sym_index,
 
 		break;
 	      }
-	    /* Fall through.  */
 	  }
+	  /* Fall through.  */
 	case 0:
 	  {
           /* We need to keep the scope around so do some locking.  This is
diff --git a/sysdeps/powerpc/powerpc64/dl-machine.h b/sysdeps/powerpc/powerpc64/dl-machine.h
index bc8bd0230e..1d926e3dff 100644
--- a/sysdeps/powerpc/powerpc64/dl-machine.h
+++ b/sysdeps/powerpc/powerpc64/dl-machine.h
@@ -902,6 +902,7 @@ elf_machine_rela (struct link_map *map,
     case R_PPC64_ADDR16_HI:
       if (dont_expect (value + 0x80000000 >= 0x100000000LL))
 	_dl_reloc_overflow (map, "R_PPC64_ADDR16_HI", reloc_addr, refsym);
+      /* Fall through.  */
     case R_PPC64_ADDR16_HIGH:
       *(Elf64_Half *) reloc_addr = PPC_HI (value);
       break;
@@ -909,6 +910,7 @@ elf_machine_rela (struct link_map *map,
     case R_PPC64_ADDR16_HA:
       if (dont_expect (value + 0x80008000 >= 0x100000000LL))
 	_dl_reloc_overflow (map, "R_PPC64_ADDR16_HA", reloc_addr, refsym);
+      /* Fall through.  */
     case R_PPC64_ADDR16_HIGHA:
       *(Elf64_Half *) reloc_addr = PPC_HA (value);
       break;
diff --git a/sysdeps/s390/iso-8859-1_cp037_z900.c b/sysdeps/s390/iso-8859-1_cp037_z900.c
index b2d8f62570..2a373fe124 100644
--- a/sysdeps/s390/iso-8859-1_cp037_z900.c
+++ b/sysdeps/s390/iso-8859-1_cp037_z900.c
@@ -227,12 +227,19 @@ __attribute__ ((aligned (8))) =
     switch (length)							\
       {									\
       case 7: outptr[6] = TABLE[inptr[6]];				\
+	/* Fall through.  */						\
       case 6: outptr[5] = TABLE[inptr[5]];				\
+	/* Fall through.  */						\
       case 5: outptr[4] = TABLE[inptr[4]];				\
+	/* Fall through.  */						\
       case 4: outptr[3] = TABLE[inptr[3]];				\
+	/* Fall through.  */						\
       case 3: outptr[2] = TABLE[inptr[2]];				\
+	/* Fall through.  */						\
       case 2: outptr[1] = TABLE[inptr[1]];				\
+	/* Fall through.  */						\
       case 1: outptr[0] = TABLE[inptr[0]];				\
+	/* Fall through.  */						\
       case 0: break;							\
       }									\
     inptr += length;							\