[PATCH] Use DIAG_IGNORE_NEEDS_COMMENT to silence -Wstringop-truncation

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Wed, Apr 25, 2018 at 10:58:59PM -0400, Carlos O'Donell wrote:
> On 04/25/2018 10:43 PM, Alan Modra wrote:
> > On Wed, Apr 25, 2018 at 07:57:22AM -0500, Carlos O'Donell wrote:
> >> Two comments here:
> >>
> >> * The FSF version of gcc should be identified here in an easy to understand way.
> >> * Consider abstracting away some of the verbose GCC_VERSION checking behind
> >>   some helper macros.
> > 
> > I'll support these ideas if/when binutils has more than a few instances
> > where we need to modify gcc diagnostics.  We have just two at the
> > moment (and two more in files generated by bison so those don't
> > count).
>  
> Mentioning the gcc version, like you did in the second version of
> the patch is very useful for future developers wanting to cleanup
> and remove old pragmas in the future when gcc 8 is no longer supported.
> It's a good habit regardless of the project or number of warnings.
> 
> But overall you're right, you don't have enough of these that it's that
> much of a problem.
> 
> Again, more of a comment, than any direct review :-)
> 

Here is the patch.  Tested with cross binutils to arm, aarch64, ppc
and s390.  OK for master?


H.J.
---
GCC 8 warns about destination size with -Wstringop-truncation:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85643

Copy DIAG_PUSH_NEEDS_COMMENT, DIAG_POP_NEEDS_COMMENT and
DIAG_IGNORE_NEEDS_COMMENT from glibc 2.27 to silence it.

	* bfd-in.h (DIAG_PUSH_NEEDS_COMMENT): New.
	(DIAG_POP_NEEDS_COMMENT): Likewse.
	(_DIAG_STR1): Likewse.
	(_DIAG_STR): Likewse.
	(DIAG_IGNORE_NEEDS_COMMENT): Likewse.
	* bfd-in2.h: Regenerated.
	* elf32-arm.c (elf32_arm_nabi_write_core_note): Use
	DIAG_PUSH_NEEDS_COMMENT, DIAG_IGNORE_NEEDS_COMMENT and
	DIAG_POP_NEEDS_COMMENT to silence GCC 8 warnings with
	-Wstringop-truncation.
	* elf32-ppc.c (ppc_elf_write_core_note): Likewse.
	* elf32-s390.c (elf_s390_write_core_note): Likewse.
	* elf64-ppc.c (ppc64_elf_write_core_note): Likewse.
	* elf64-s390.c (elf_s390_write_core_note): Likewse.
	* elfxx-aarch64.c (_bfd_aarch64_elf_write_core_note): Likewse.
---
 bfd/bfd-in.h        | 38 ++++++++++++++++++++++++++++++++++++++
 bfd/bfd-in2.h       | 38 ++++++++++++++++++++++++++++++++++++++
 bfd/elf32-arm.c     |  9 +++++++++
 bfd/elf32-ppc.c     |  9 +++++++++
 bfd/elf32-s390.c    |  9 +++++++++
 bfd/elf64-ppc.c     |  9 +++++++++
 bfd/elf64-s390.c    |  9 +++++++++
 bfd/elfxx-aarch64.c |  9 +++++++++
 8 files changed, 130 insertions(+)

diff --git a/bfd/bfd-in.h b/bfd/bfd-in.h
index 50a8b52e96..5d9e311081 100644
--- a/bfd/bfd-in.h
+++ b/bfd/bfd-in.h
@@ -71,6 +71,44 @@ extern "C" {
 #define LITMEMCPY(DEST,STR2) memcpy ((DEST), (STR2), sizeof (STR2) - 1)
 #define LITSTRCPY(DEST,STR2) memcpy ((DEST), (STR2), sizeof (STR2))
 
+#if __GNUC__ >= 8
+/* These are copied from glibc 2.27.  */
+
+/* The macros to control diagnostics are structured like this, rather
+   than a single macro that both pushes and pops diagnostic state and
+   takes the affected code as an argument, because the GCC pragmas
+   work by disabling the diagnostic for a range of source locations
+   and do not work when all the pragmas and the affected code are in a
+   single macro expansion.  */
+
+/* Push diagnostic state.  */
+#define DIAG_PUSH_NEEDS_COMMENT _Pragma ("GCC diagnostic push")
+
+/* Pop diagnostic state.  */
+#define DIAG_POP_NEEDS_COMMENT _Pragma ("GCC diagnostic pop")
+
+#define _DIAG_STR1(s) #s
+#define _DIAG_STR(s) _DIAG_STR1(s)
+
+/* Ignore the diagnostic OPTION.  VERSION is the most recent GCC
+   version for which the diagnostic has been confirmed to appear in
+   the absence of the pragma (in the form MAJOR.MINOR for GCC 4.x,
+   just MAJOR for GCC 5 and later).  Uses of this pragma should be
+   reviewed when the GCC version given is no longer supported for
+   building glibc; the version number should always be on the same
+   source line as the macro name, so such uses can be found with grep.
+   Uses should come with a comment giving more details of the
+   diagnostic, and an architecture on which it is seen if possibly
+   optimization-related and not in architecture-specific code.  This
+   macro should only be used if the diagnostic seems hard to fix (for
+   example, optimization-related false positives).  */
+#define DIAG_IGNORE_NEEDS_COMMENT(version, option)     \
+  _Pragma (_DIAG_STR (GCC diagnostic ignored option))
+#else
+#define DIAG_PUSH_NEEDS_COMMENT
+#define DIAG_POP_NEEDS_COMMENT
+#define DIAG_IGNORE_NEEDS_COMMENT(version, option)
+#endif
 
 #define BFD_SUPPORTS_PLUGINS @supports_plugins@
 
diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index 48226860c7..9bee17bad5 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -78,6 +78,44 @@ extern "C" {
 #define LITMEMCPY(DEST,STR2) memcpy ((DEST), (STR2), sizeof (STR2) - 1)
 #define LITSTRCPY(DEST,STR2) memcpy ((DEST), (STR2), sizeof (STR2))
 
+#if __GNUC__ >= 8
+/* These are copied from glibc 2.27.  */
+
+/* The macros to control diagnostics are structured like this, rather
+   than a single macro that both pushes and pops diagnostic state and
+   takes the affected code as an argument, because the GCC pragmas
+   work by disabling the diagnostic for a range of source locations
+   and do not work when all the pragmas and the affected code are in a
+   single macro expansion.  */
+
+/* Push diagnostic state.  */
+#define DIAG_PUSH_NEEDS_COMMENT _Pragma ("GCC diagnostic push")
+
+/* Pop diagnostic state.  */
+#define DIAG_POP_NEEDS_COMMENT _Pragma ("GCC diagnostic pop")
+
+#define _DIAG_STR1(s) #s
+#define _DIAG_STR(s) _DIAG_STR1(s)
+
+/* Ignore the diagnostic OPTION.  VERSION is the most recent GCC
+   version for which the diagnostic has been confirmed to appear in
+   the absence of the pragma (in the form MAJOR.MINOR for GCC 4.x,
+   just MAJOR for GCC 5 and later).  Uses of this pragma should be
+   reviewed when the GCC version given is no longer supported for
+   building glibc; the version number should always be on the same
+   source line as the macro name, so such uses can be found with grep.
+   Uses should come with a comment giving more details of the
+   diagnostic, and an architecture on which it is seen if possibly
+   optimization-related and not in architecture-specific code.  This
+   macro should only be used if the diagnostic seems hard to fix (for
+   example, optimization-related false positives).  */
+#define DIAG_IGNORE_NEEDS_COMMENT(version, option)     \
+  _Pragma (_DIAG_STR (GCC diagnostic ignored option))
+#else
+#define DIAG_PUSH_NEEDS_COMMENT
+#define DIAG_POP_NEEDS_COMMENT
+#define DIAG_IGNORE_NEEDS_COMMENT(version, option)
+#endif
 
 #define BFD_SUPPORTS_PLUGINS @supports_plugins@
 
diff --git a/bfd/elf32-arm.c b/bfd/elf32-arm.c
index 5a3b58ff0d..da8a528e36 100644
--- a/bfd/elf32-arm.c
+++ b/bfd/elf32-arm.c
@@ -2174,7 +2174,16 @@ elf32_arm_nabi_write_core_note (bfd *abfd, char *buf, int *bufsiz,
 	va_start (ap, note_type);
 	memset (data, 0, sizeof (data));
 	strncpy (data + 28, va_arg (ap, const char *), 16);
+	DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (8, 0)
+	/* GCC 8 warns about 80 equals destination size with
+	   -Wstringop-truncation:
+	   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85643
+	 */
+	DIAG_IGNORE_NEEDS_COMMENT (8, "-Wstringop-truncation");
+#endif
 	strncpy (data + 44, va_arg (ap, const char *), 80);
+	DIAG_POP_NEEDS_COMMENT;
 	va_end (ap);
 
 	return elfcore_write_note (abfd, buf, bufsiz,
diff --git a/bfd/elf32-ppc.c b/bfd/elf32-ppc.c
index 462c8af311..c8ddcffdac 100644
--- a/bfd/elf32-ppc.c
+++ b/bfd/elf32-ppc.c
@@ -2411,7 +2411,16 @@ ppc_elf_write_core_note (bfd *abfd, char *buf, int *bufsiz, int note_type, ...)
 	va_start (ap, note_type);
 	memset (data, 0, sizeof (data));
 	strncpy (data + 32, va_arg (ap, const char *), 16);
+	DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (8, 0)
+	/* GCC 8 warns about 80 equals destination size with
+	   -Wstringop-truncation:
+	   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85643
+	 */
+	DIAG_IGNORE_NEEDS_COMMENT (8, "-Wstringop-truncation");
+#endif
 	strncpy (data + 48, va_arg (ap, const char *), 80);
+	DIAG_POP_NEEDS_COMMENT;
 	va_end (ap);
 	return elfcore_write_note (abfd, buf, bufsiz,
 				   "CORE", note_type, data, sizeof (data));
diff --git a/bfd/elf32-s390.c b/bfd/elf32-s390.c
index b3603bd865..60433a38e5 100644
--- a/bfd/elf32-s390.c
+++ b/bfd/elf32-s390.c
@@ -3951,7 +3951,16 @@ elf_s390_write_core_note (bfd *abfd, char *buf, int *bufsiz,
 	va_end (ap);
 
 	strncpy (data + 28, fname, 16);
+	DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (8, 0)
+	/* GCC 8 warns about 80 equals destination size with
+	   -Wstringop-truncation:
+	   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85643
+	 */
+	DIAG_IGNORE_NEEDS_COMMENT (8, "-Wstringop-truncation");
+#endif
 	strncpy (data + 44, psargs, 80);
+	DIAG_POP_NEEDS_COMMENT;
 	return elfcore_write_note (abfd, buf, bufsiz, "CORE", note_type,
 				   &data, sizeof (data));
       }
diff --git a/bfd/elf64-ppc.c b/bfd/elf64-ppc.c
index 09377d102c..91c5edae20 100644
--- a/bfd/elf64-ppc.c
+++ b/bfd/elf64-ppc.c
@@ -3041,7 +3041,16 @@ ppc64_elf_write_core_note (bfd *abfd, char *buf, int *bufsiz, int note_type,
 	va_start (ap, note_type);
 	memset (data, 0, sizeof (data));
 	strncpy (data + 40, va_arg (ap, const char *), 16);
+	DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (8, 0)
+	/* GCC 8 warns about 80 equals destination size with
+	   -Wstringop-truncation:
+	   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85643
+	 */
+	DIAG_IGNORE_NEEDS_COMMENT (8, "-Wstringop-truncation");
+#endif
 	strncpy (data + 56, va_arg (ap, const char *), 80);
+	DIAG_POP_NEEDS_COMMENT;
 	va_end (ap);
 	return elfcore_write_note (abfd, buf, bufsiz,
 				   "CORE", note_type, data, sizeof (data));
diff --git a/bfd/elf64-s390.c b/bfd/elf64-s390.c
index bfa02340ca..1773c208b4 100644
--- a/bfd/elf64-s390.c
+++ b/bfd/elf64-s390.c
@@ -3760,7 +3760,16 @@ elf_s390_write_core_note (bfd *abfd, char *buf, int *bufsiz,
 	va_end (ap);
 
 	strncpy (data + 40, fname, 16);
+	DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (8, 0)
+	/* GCC 8 warns about 80 equals destination size with
+	   -Wstringop-truncation:
+	   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85643
+	 */
+	DIAG_IGNORE_NEEDS_COMMENT (8, "-Wstringop-truncation");
+#endif
 	strncpy (data + 56, psargs, 80);
+	DIAG_POP_NEEDS_COMMENT;
 	return elfcore_write_note (abfd, buf, bufsiz, "CORE", note_type,
 				   &data, sizeof (data));
       }
diff --git a/bfd/elfxx-aarch64.c b/bfd/elfxx-aarch64.c
index 45a732db2b..6450c5f1c6 100644
--- a/bfd/elfxx-aarch64.c
+++ b/bfd/elfxx-aarch64.c
@@ -659,7 +659,16 @@ _bfd_aarch64_elf_write_core_note (bfd *abfd, char *buf, int *bufsiz, int note_ty
 	va_start (ap, note_type);
 	memset (data, 0, sizeof (data));
 	strncpy (data + 40, va_arg (ap, const char *), 16);
+	DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (8, 0)
+	/* GCC 8 warns about 80 equals destination size with
+	   -Wstringop-truncation:
+	   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85643
+	 */
+	DIAG_IGNORE_NEEDS_COMMENT (8, "-Wstringop-truncation");
+#endif
 	strncpy (data + 56, va_arg (ap, const char *), 80);
+	DIAG_POP_NEEDS_COMMENT;
 	va_end (ap);
 
 	return elfcore_write_note (abfd, buf, bufsiz, "CORE",
-- 
2.17.0