Silence gcc-8 warnings

Alan Modra amodra@gmail.com
Wed Apr 25 07:54:00 GMT 2018


On Mon, Apr 23, 2018 at 02:54:42AM -0600, Jan Beulich wrote:
> >>> On 23.04.18 at 10:48, <amodra@gmail.com> wrote:
> > --- a/bfd/elf-linux-core.h
> > +++ b/bfd/elf-linux-core.h
> > @@ -69,8 +69,12 @@ swap_linux_prpsinfo32_ugid32_out
> >    bfd_put_32 (obfd, from->pr_ppid, to->pr_ppid);
> >    bfd_put_32 (obfd, from->pr_pgrp, to->pr_pgrp);
> >    bfd_put_32 (obfd, from->pr_sid, to->pr_sid);
> > +#pragma GCC diagnostic push
> > +#pragma GCC diagnostic ignored "-Wpragmas"
> > +#pragma GCC diagnostic ignored "-Wstringop-truncation"
> >    strncpy (to->pr_fname, from->pr_fname, sizeof (to->pr_fname));
> >    strncpy (to->pr_psargs, from->pr_psargs, sizeof (to->pr_psargs));
> > +#pragma GCC diagnostic pop
> >  }
> 
> We've tried to use this approach in the Xen hypervisor sources too in at least
> one place: Older gcc isn't happy about such #pragma-s inside functions. Sadly
> we haven't found a neat alternative (yet).

This seems to work with gcc-8 and a bunch of prior gcc versions I tested.

	* elf-linux-core.h: Disable gcc-8 string truncation warning.
	* elf.c (elfcore_write_prpsinfo): Likewise.

diff --git a/bfd/elf-linux-core.h b/bfd/elf-linux-core.h
index 0a5d76f..453b9e0 100644
--- a/bfd/elf-linux-core.h
+++ b/bfd/elf-linux-core.h
@@ -21,6 +21,25 @@
 #ifndef ELF_LINUX_CORE_H
 #define ELF_LINUX_CORE_H
 
+/* gcc-8 warns (*) on all the strncpy calls in this file about
+   possible string truncation.  The "truncation" is not a bug.  We
+   have an external representation of structs with fields that are not
+   necessarily NULL terminated and corresponding internal
+   representation fields that are one larger so that they can always
+   be NULL terminated.
+   gcc versions between 4.2 and 4.6 do not allow pragma control of
+   diagnostics inside functions, giving a hard error if you try to use
+   the finer control available with later versions.
+   gcc prior to 4.2 warns about diagnostic push and pop.
+   gcc-5, gcc-6 and gcc-7 warn that -Wstringop-truncation is unknown,
+   unless you also add #pragma GCC diagnostic ignored "-Wpragma".
+   (*) Depending on your system header files!  */
+
+#if GCC_VERSION >= 8000
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstringop-truncation"
+#endif
+
 /* External 32-bit structure for PRPSINFO.  This structure is
    ABI-defined, thus we choose to use char arrays here in order to
    avoid dealing with different types in different architectures.
@@ -231,4 +250,8 @@ swap_linux_prpsinfo64_ugid16_out
   strncpy (to->pr_psargs, from->pr_psargs, sizeof (to->pr_psargs));
 }
 
+#if GCC_VERSION >= 8000
+#pragma GCC diagnostic pop
+#endif
+
 #endif
diff --git a/bfd/elf.c b/bfd/elf.c
index 092b275..bd9ffcc 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -10508,6 +10508,10 @@ elfcore_write_note (bfd *abfd,
   return buf;
 }
 
+#if GCC_VERSION >= 8000
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstringop-truncation"
+#endif
 char *
 elfcore_write_prpsinfo (bfd  *abfd,
 			char *buf,
@@ -10566,6 +10570,9 @@ elfcore_write_prpsinfo (bfd  *abfd,
   free (buf);
   return NULL;
 }
+#if GCC_VERSION >= 8000
+#pragma GCC diagnostic pop
+#endif
 
 char *
 elfcore_write_linux_prpsinfo32


-- 
Alan Modra
Australia Development Lab, IBM



More information about the Binutils mailing list