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
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