-Wstringop-truncation warnings

Message ID 20180504093248.GG28782@bubble.grove.modra.org
State New
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  • -Wstringop-truncation warnings
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Commit Message

Alan Modra May 4, 2018, 9:32 a.m.
This patch is aimed at silencing gcc8 -Wstringop-truncation warnings.

Unfortunately adding  __attribute__ ((__nonstring)) doesn't work in a
number of the places patched here, (see
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85643) so if you have
recent glibc headers installed you'll need to configure binutils with
--disable-werror to compile using gcc8 or gcc9.

include/
	* ansidecl.h: Import from gcc.
	* coff/internal.h (struct internal_scnhdr): Add ATTRIBUTE_NONSTRING
	to s_name.
	(struct internal_syment): Add ATTRIBUTE_NONSTRING to _n_name.
bfd/
	* elf-linux-core.h (struct elf_external_linux_prpsinfo32_ugid32),
	(struct elf_external_linux_prpsinfo32_ugid16),
	(struct elf_external_linux_prpsinfo64_ugid32),
	(struct elf_external_linux_prpsinfo64_ugid16): Add ATTRIBUTE_NONSTRING
	to pr_fname and pr_psargs fields.  Remove GCC diagnostic pragmas.
	Move comment to..
	* elf.c (elfcore_write_prpsinfo): ..here.  Indent nested preprocessor
	directives.
	* elf32-arm.c (elf32_arm_nabi_write_core_note): Add ATTRIBUTE_NONSTRING
	to data.
	* elf32-ppc.c (ppc_elf_write_core_note): Likewise.
	* elf32-s390.c (elf_s390_write_core_note): Likewise.
	* elf64-s390.c (elf_s390_write_core_note): Likewise.
	* elfxx-aarch64.c (_bfd_aarch64_elf_write_core_note): Likewise.
	* elf64-x86-64.c (elf_x86_64_write_core_note): Add GCC diagnostic
	pragmas.
	* peXXigen.c (_bfd_XXi_swap_scnhdr_out): Use strnlen to avoid
	false positive gcc-8 warning.
gas/
	* config/obj-evax.c (shorten_identifier): Use memcpy in place
	of strncpy.
	* config/obj-macho.c (obj_mach_o_make_or_get_sect): Ensure
	segname and sectname fields are NUL terminated.


-- 
Alan Modra
Australia Development Lab, IBM

Comments

H.J. Lu May 7, 2018, 12:15 a.m. | #1
On Fri, May 4, 2018 at 2:32 AM, Alan Modra <amodra@gmail.com> wrote:
> This patch is aimed at silencing gcc8 -Wstringop-truncation warnings.

>

> Unfortunately adding  __attribute__ ((__nonstring)) doesn't work in a

> number of the places patched here, (see

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85643) so if you have

> recent glibc headers installed you'll need to configure binutils with

> --disable-werror to compile using gcc8 or gcc9.

>

> include/

>         * ansidecl.h: Import from gcc.

>         * coff/internal.h (struct internal_scnhdr): Add ATTRIBUTE_NONSTRING

>         to s_name.

>         (struct internal_syment): Add ATTRIBUTE_NONSTRING to _n_name.

> bfd/

>         * elf-linux-core.h (struct elf_external_linux_prpsinfo32_ugid32),

>         (struct elf_external_linux_prpsinfo32_ugid16),

>         (struct elf_external_linux_prpsinfo64_ugid32),

>         (struct elf_external_linux_prpsinfo64_ugid16): Add ATTRIBUTE_NONSTRING

>         to pr_fname and pr_psargs fields.  Remove GCC diagnostic pragmas.

>         Move comment to..

>         * elf.c (elfcore_write_prpsinfo): ..here.  Indent nested preprocessor

>         directives.

>         * elf32-arm.c (elf32_arm_nabi_write_core_note): Add ATTRIBUTE_NONSTRING

>         to data.

>         * elf32-ppc.c (ppc_elf_write_core_note): Likewise.

>         * elf32-s390.c (elf_s390_write_core_note): Likewise.

>         * elf64-s390.c (elf_s390_write_core_note): Likewise.

>         * elfxx-aarch64.c (_bfd_aarch64_elf_write_core_note): Likewise.

>         * elf64-x86-64.c (elf_x86_64_write_core_note): Add GCC diagnostic

>         pragmas.

>         * peXXigen.c (_bfd_XXi_swap_scnhdr_out): Use strnlen to avoid

>         false positive gcc-8 warning.

> gas/

>         * config/obj-evax.c (shorten_identifier): Use memcpy in place

>         of strncpy.

>         * config/obj-macho.c (obj_mach_o_make_or_get_sect): Ensure

>         segname and sectname fields are NUL terminated.

>

> diff --git a/bfd/cofflink.c b/bfd/cofflink.c

> index fb1696afff..6ca547ce5b 100644

> --- a/bfd/cofflink.c

> +++ b/bfd/cofflink.c

> @@ -1839,7 +1839,7 @@ _bfd_coff_link_input_bfd (struct coff_final_link_info *flaginfo, bfd *input_bfd)

>

>             case C_FCN:

>               if (obj_pe (input_bfd)

> -                 && strcmp (isym.n_name, ".bf") != 0

> +                 && strncmp (isym.n_name, ".bf", sizeof isym.n_name) != 0

>                   && isym.n_scnum > 0)

>                 {

>                   /* For PE, .lf and .ef get their value left alone,


If this is truly non-string, can memcmp be used instead?


-- 
H.J.
Alan Modra May 7, 2018, 2:23 a.m. | #2
On Sun, May 06, 2018 at 05:15:22PM -0700, H.J. Lu wrote:
> On Fri, May 4, 2018 at 2:32 AM, Alan Modra <amodra@gmail.com> wrote:

> > index fb1696afff..6ca547ce5b 100644

> > --- a/bfd/cofflink.c

> > +++ b/bfd/cofflink.c

> > @@ -1839,7 +1839,7 @@ _bfd_coff_link_input_bfd (struct coff_final_link_info *flaginfo, bfd *input_bfd)

> >

> >             case C_FCN:

> >               if (obj_pe (input_bfd)

> > -                 && strcmp (isym.n_name, ".bf") != 0

> > +                 && strncmp (isym.n_name, ".bf", sizeof isym.n_name) != 0

> >                   && isym.n_scnum > 0)

> >                 {

> >                   /* For PE, .lf and .ef get their value left alone,

> 

> If this is truly non-string, can memcmp be used instead?


Yes, good idea.  That would avoid avoid
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85623 for these strncpy
calls.  I'll commit the following after running my usual tests, and
fix the missing ChangeLog entry for cofflink.c.

	* cofflink.c (_bfd_coff_link_input_bfd): Use memcmp rather than
	strncmp when checking for ".bf" special symbol.
	* prXXigen.c (_bfd_XXi_swap_scnhdr_out): Make pe_required_section_flags
	section_name a char array, remove sentinal known_sections entry,
	and adjust loop over known_sections to suit.  Use memcmp rather
	than strncmp.

diff --git a/bfd/cofflink.c b/bfd/cofflink.c
index 6ca547ce5b..2f73f72e31 100644
--- a/bfd/cofflink.c
+++ b/bfd/cofflink.c
@@ -1839,7 +1839,7 @@ _bfd_coff_link_input_bfd (struct coff_final_link_info *flaginfo, bfd *input_bfd)
 
 	    case C_FCN:
 	      if (obj_pe (input_bfd)
-		  && strncmp (isym.n_name, ".bf", sizeof isym.n_name) != 0
+		  && memcmp (isym.n_name, ".bf", sizeof ".bf") != 0
 		  && isym.n_scnum > 0)
 		{
 		  /* For PE, .lf and .ef get their value left alone,
diff --git a/bfd/peXXigen.c b/bfd/peXXigen.c
index a62d126aff..5e0acc4571 100644
--- a/bfd/peXXigen.c
+++ b/bfd/peXXigen.c
@@ -1018,7 +1018,7 @@ _bfd_XXi_swap_scnhdr_out (bfd * abfd, void * in, void * out)
 
     typedef struct
     {
-      const char *	section_name;
+      char section_name[SCNNMLEN];
       unsigned long	must_have;
     }
     pe_required_section_flags;
@@ -1037,7 +1037,6 @@ _bfd_XXi_swap_scnhdr_out (bfd * abfd, void * in, void * out)
 	{ ".text" , IMAGE_SCN_MEM_READ | IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE },
 	{ ".tls",   IMAGE_SCN_MEM_READ | IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_WRITE },
 	{ ".xdata", IMAGE_SCN_MEM_READ | IMAGE_SCN_CNT_INITIALIZED_DATA },
-	{ NULL, 0}
       };
 
     pe_required_section_flags * p;
@@ -1050,11 +1049,12 @@ _bfd_XXi_swap_scnhdr_out (bfd * abfd, void * in, void * out)
        by ld --enable-auto-import (if auto-import is actually needed),
        by ld --omagic, or by obcopy --writable-text.  */
 
-    for (p = known_sections; p->section_name; p++)
-      if (strncmp (scnhdr_int->s_name, p->section_name,
-		   sizeof scnhdr_int->s_name) == 0)
+    for (p = known_sections;
+	 p < known_sections + ARRAY_SIZE (known_sections);
+	 p++)
+      if (memcmp (scnhdr_int->s_name, p->section_name, SCNNMLEN) == 0)
 	{
-	  if (strncmp (scnhdr_int->s_name, ".text", sizeof scnhdr_int->s_name)
+	  if (memcmp (scnhdr_int->s_name, ".text", sizeof ".text")
 	      || (bfd_get_file_flags (abfd) & WP_TEXT))
 	    scnhdr_int->s_flags &= ~IMAGE_SCN_MEM_WRITE;
 	  scnhdr_int->s_flags |= p->must_have;
@@ -1067,7 +1067,7 @@ _bfd_XXi_swap_scnhdr_out (bfd * abfd, void * in, void * out)
   if (coff_data (abfd)->link_info
       && ! bfd_link_relocatable (coff_data (abfd)->link_info)
       && ! bfd_link_pic (coff_data (abfd)->link_info)
-      && strncmp (scnhdr_int->s_name, ".text", sizeof scnhdr_int->s_name) == 0)
+      && memcmp (scnhdr_int->s_name, ".text", sizeof ".text") == 0)
     {
       /* By inference from looking at MS output, the 32 bit field
 	 which is the combination of the number_of_relocs and
Alan Modra May 7, 2018, 8:39 a.m. | #3
On Mon, May 07, 2018 at 02:24:44AM -0400, DJ Delorie wrote:
> 

> Alan Modra <amodra@gmail.com> writes:

> > -		  && strncmp (isym.n_name, ".bf", sizeof isym.n_name) != 0

> > +		  && memcmp (isym.n_name, ".bf", sizeof ".bf") != 0

> 

> Is this really the same if isym.n_name[] is ".bf1234\0\0" ?


Yes.  sizeof ".bf" is 4, so the NUL is included.

-- 
Alan Modra
Australia Development Lab, IBM
H.J. Lu May 23, 2018, 5:18 p.m. | #4
On Fri, May 4, 2018 at 2:32 AM, Alan Modra <amodra@gmail.com> wrote:
> This patch is aimed at silencing gcc8 -Wstringop-truncation warnings.

>

> Unfortunately adding  __attribute__ ((__nonstring)) doesn't work in a

> number of the places patched here, (see

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85643) so if you have

> recent glibc headers installed you'll need to configure binutils with

> --disable-werror to compile using gcc8 or gcc9.

>

> include/

>         * ansidecl.h: Import from gcc.

>         * coff/internal.h (struct internal_scnhdr): Add ATTRIBUTE_NONSTRING

>         to s_name.

>         (struct internal_syment): Add ATTRIBUTE_NONSTRING to _n_name.

> bfd/

>         * elf-linux-core.h (struct elf_external_linux_prpsinfo32_ugid32),

>         (struct elf_external_linux_prpsinfo32_ugid16),

>         (struct elf_external_linux_prpsinfo64_ugid32),

>         (struct elf_external_linux_prpsinfo64_ugid16): Add ATTRIBUTE_NONSTRING

>         to pr_fname and pr_psargs fields.  Remove GCC diagnostic pragmas.

>         Move comment to..

>         * elf.c (elfcore_write_prpsinfo): ..here.  Indent nested preprocessor

>         directives.

>         * elf32-arm.c (elf32_arm_nabi_write_core_note): Add ATTRIBUTE_NONSTRING

>         to data.

>         * elf32-ppc.c (ppc_elf_write_core_note): Likewise.

>         * elf32-s390.c (elf_s390_write_core_note): Likewise.

>         * elf64-s390.c (elf_s390_write_core_note): Likewise.

>         * elfxx-aarch64.c (_bfd_aarch64_elf_write_core_note): Likewise.

>         * elf64-x86-64.c (elf_x86_64_write_core_note): Add GCC diagnostic

>         pragmas.

>         * peXXigen.c (_bfd_XXi_swap_scnhdr_out): Use strnlen to avoid

>         false positive gcc-8 warning.

> gas/

>         * config/obj-evax.c (shorten_identifier): Use memcpy in place

>         of strncpy.

>         * config/obj-macho.c (obj_mach_o_make_or_get_sect): Ensure

>         segname and sectname fields are NUL terminated.

>


I checked in this one.

-- 
H.J.
--
From 9ef6d1e31f380349c8f329d1adb47ee53ec1f6c2 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>

Date: Wed, 23 May 2018 10:15:11 -0700
Subject: [PATCH] Add ATTRIBUTE_NONSTRING to ppc64_elf_write_core_note

This patch silences gcc8 -Wstringop-truncation warnings.

* elf64-ppc.c (ppc64_elf_write_core_note): Add ATTRIBUTE_NONSTRING
to data.
---
 bfd/ChangeLog   | 5 +++++
 bfd/elf64-ppc.c | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 1f6a85f7e0..f086ad59c1 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,8 @@
+2018-05-23  H.J. Lu  <hongjiu.lu@intel.com>
+
+ * elf64-ppc.c (ppc64_elf_write_core_note): Add ATTRIBUTE_NONSTRING
+ to data.
+
 2018-05-22  Alan Modra  <amodra@gmail.com>

  PR 23207
diff --git a/bfd/elf64-ppc.c b/bfd/elf64-ppc.c
index b166558945..7f7a8f777e 100644
--- a/bfd/elf64-ppc.c
+++ b/bfd/elf64-ppc.c
@@ -3035,7 +3035,7 @@ ppc64_elf_write_core_note (bfd *abfd, char *buf,
int *bufsiz, int note_type,

     case NT_PRPSINFO:
       {
- char data[136];
+ char data[136] ATTRIBUTE_NONSTRING;
  va_list ap;

  va_start (ap, note_type);
-- 
2.17.0
Alan Modra May 23, 2018, 11:05 p.m. | #5
On Wed, May 23, 2018 at 10:18:20AM -0700, H.J. Lu wrote:
> * elf64-ppc.c (ppc64_elf_write_core_note): Add ATTRIBUTE_NONSTRING

> to data.


Thanks!  (I wonder how I missed seeing that one??)

-- 
Alan Modra
Australia Development Lab, IBM

Patch

diff --git a/bfd/cofflink.c b/bfd/cofflink.c
index fb1696afff..6ca547ce5b 100644
--- a/bfd/cofflink.c
+++ b/bfd/cofflink.c
@@ -1839,7 +1839,7 @@  _bfd_coff_link_input_bfd (struct coff_final_link_info *flaginfo, bfd *input_bfd)
 
 	    case C_FCN:
 	      if (obj_pe (input_bfd)
-		  && strcmp (isym.n_name, ".bf") != 0
+		  && strncmp (isym.n_name, ".bf", sizeof isym.n_name) != 0
 		  && isym.n_scnum > 0)
 		{
 		  /* For PE, .lf and .ef get their value left alone,
diff --git a/bfd/elf-linux-core.h b/bfd/elf-linux-core.h
index fa0690320a..f0c4b2fc35 100644
--- a/bfd/elf-linux-core.h
+++ b/bfd/elf-linux-core.h
@@ -21,25 +21,6 @@ 
 #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.
@@ -64,8 +45,8 @@  struct elf_external_linux_prpsinfo32_ugid32
     char pr_ppid[4];
     char pr_pgrp[4];
     char pr_sid[4];
-    char pr_fname[16];			/* Filename of executable.  */
-    char pr_psargs[80];			/* Initial part of arg list.  */
+    char pr_fname[16] ATTRIBUTE_NONSTRING;  /* Filename of executable.  */
+    char pr_psargs[80] ATTRIBUTE_NONSTRING; /* Initial part of arg list.  */
   };
 
 /* Helper function to copy an elf_internal_linux_prpsinfo in host
@@ -116,8 +97,8 @@  struct elf_external_linux_prpsinfo32_ugid16
     char pr_ppid[4];
     char pr_pgrp[4];
     char pr_sid[4];
-    char pr_fname[16];			/* Filename of executable.  */
-    char pr_psargs[80];			/* Initial part of arg list.  */
+    char pr_fname[16] ATTRIBUTE_NONSTRING;  /* Filename of executable.  */
+    char pr_psargs[80] ATTRIBUTE_NONSTRING; /* Initial part of arg list.  */
   };
 
 /* Helper function to copy an elf_internal_linux_prpsinfo in host
@@ -169,8 +150,8 @@  struct elf_external_linux_prpsinfo64_ugid32
     char pr_ppid[4];
     char pr_pgrp[4];
     char pr_sid[4];
-    char pr_fname[16];			/* Filename of executable.  */
-    char pr_psargs[80];			/* Initial part of arg list.  */
+    char pr_fname[16] ATTRIBUTE_NONSTRING;  /* Filename of executable.  */
+    char pr_psargs[80] ATTRIBUTE_NONSTRING; /* Initial part of arg list.  */
   };
 
 /* Helper function to copy an elf_internal_linux_prpsinfo in host
@@ -222,8 +203,8 @@  struct elf_external_linux_prpsinfo64_ugid16
     char pr_ppid[4];
     char pr_pgrp[4];
     char pr_sid[4];
-    char pr_fname[16];			/* Filename of executable.  */
-    char pr_psargs[80];			/* Initial part of arg list.  */
+    char pr_fname[16] ATTRIBUTE_NONSTRING;  /* Filename of executable.  */
+    char pr_psargs[80] ATTRIBUTE_NONSTRING; /* Initial part of arg list.  */
   };
 
 /* Helper function to copy an elf_internal_linux_prpsinfo in host
@@ -250,8 +231,4 @@  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 bd9ffccee6..21bc4e7ac2 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -10508,9 +10508,22 @@  elfcore_write_note (bfd *abfd,
   return buf;
 }
 
+/* gcc-8 warns (*) on all the strncpy calls in this function 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"
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wstringop-truncation"
 #endif
 char *
 elfcore_write_prpsinfo (bfd  *abfd,
@@ -10531,16 +10544,16 @@  elfcore_write_prpsinfo (bfd  *abfd,
     }
 
 #if defined (HAVE_PRPSINFO_T) || defined (HAVE_PSINFO_T)
-#if defined (HAVE_PRPSINFO32_T) || defined (HAVE_PSINFO32_T)
+# if defined (HAVE_PRPSINFO32_T) || defined (HAVE_PSINFO32_T)
   if (bed->s->elfclass == ELFCLASS32)
     {
-#if defined (HAVE_PSINFO32_T)
+#  if defined (HAVE_PSINFO32_T)
       psinfo32_t data;
       int note_type = NT_PSINFO;
-#else
+#  else
       prpsinfo32_t data;
       int note_type = NT_PRPSINFO;
-#endif
+#  endif
 
       memset (&data, 0, sizeof (data));
       strncpy (data.pr_fname, fname, sizeof (data.pr_fname));
@@ -10549,15 +10562,15 @@  elfcore_write_prpsinfo (bfd  *abfd,
 				 "CORE", note_type, &data, sizeof (data));
     }
   else
-#endif
+# endif
     {
-#if defined (HAVE_PSINFO_T)
+# if defined (HAVE_PSINFO_T)
       psinfo_t data;
       int note_type = NT_PSINFO;
-#else
+# else
       prpsinfo_t data;
       int note_type = NT_PRPSINFO;
-#endif
+# endif
 
       memset (&data, 0, sizeof (data));
       strncpy (data.pr_fname, fname, sizeof (data.pr_fname));
@@ -10571,7 +10584,7 @@  elfcore_write_prpsinfo (bfd  *abfd,
   return NULL;
 }
 #if GCC_VERSION >= 8000
-#pragma GCC diagnostic pop
+# pragma GCC diagnostic pop
 #endif
 
 char *
diff --git a/bfd/elf32-arm.c b/bfd/elf32-arm.c
index a42db44b2f..5a3b58ff0d 100644
--- a/bfd/elf32-arm.c
+++ b/bfd/elf32-arm.c
@@ -2168,7 +2168,7 @@  elf32_arm_nabi_write_core_note (bfd *abfd, char *buf, int *bufsiz,
 
     case NT_PRPSINFO:
       {
-	char data[124];
+	char data[124] ATTRIBUTE_NONSTRING;
 	va_list ap;
 
 	va_start (ap, note_type);
diff --git a/bfd/elf32-ppc.c b/bfd/elf32-ppc.c
index 7f4ed01f20..462c8af311 100644
--- a/bfd/elf32-ppc.c
+++ b/bfd/elf32-ppc.c
@@ -2405,7 +2405,7 @@  ppc_elf_write_core_note (bfd *abfd, char *buf, int *bufsiz, int note_type, ...)
 
     case NT_PRPSINFO:
       {
-	char data[128];
+	char data[128] ATTRIBUTE_NONSTRING;
 	va_list ap;
 
 	va_start (ap, note_type);
diff --git a/bfd/elf32-s390.c b/bfd/elf32-s390.c
index 18010c0b45..b3603bd865 100644
--- a/bfd/elf32-s390.c
+++ b/bfd/elf32-s390.c
@@ -3942,7 +3942,7 @@  elf_s390_write_core_note (bfd *abfd, char *buf, int *bufsiz,
 
     case NT_PRPSINFO:
       {
-	char data[124] = { 0 };
+	char data[124] ATTRIBUTE_NONSTRING = { 0 };
 	const char *fname, *psargs;
 
 	va_start (ap, note_type);
diff --git a/bfd/elf64-s390.c b/bfd/elf64-s390.c
index 2d02e82c54..bfa02340ca 100644
--- a/bfd/elf64-s390.c
+++ b/bfd/elf64-s390.c
@@ -3751,7 +3751,7 @@  elf_s390_write_core_note (bfd *abfd, char *buf, int *bufsiz,
 
     case NT_PRPSINFO:
       {
-	char data[136] = { 0 };
+	char data[136] ATTRIBUTE_NONSTRING = { 0 };
 	const char *fname, *psargs;
 
 	va_start (ap, note_type);
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index c1237bb2e4..a0ebd2cf69 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -439,6 +439,10 @@  elf_x86_64_grok_psinfo (bfd *abfd, Elf_Internal_Note *note)
 }
 
 #ifdef CORE_HEADER
+# if GCC_VERSION >= 8000
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wstringop-truncation"
+# endif
 static char *
 elf_x86_64_write_core_note (bfd *abfd, char *buf, int *bufsiz,
 			    int note_type, ...)
@@ -524,6 +528,9 @@  elf_x86_64_write_core_note (bfd *abfd, char *buf, int *bufsiz,
     }
   /* NOTREACHED */
 }
+# if GCC_VERSION >= 8000
+#  pragma GCC diagnostic pop
+# endif
 #endif
 
 /* Functions for the x86-64 ELF linker.	 */
diff --git a/bfd/elfxx-aarch64.c b/bfd/elfxx-aarch64.c
index 08e7cd9684..45a732db2b 100644
--- a/bfd/elfxx-aarch64.c
+++ b/bfd/elfxx-aarch64.c
@@ -653,7 +653,7 @@  _bfd_aarch64_elf_write_core_note (bfd *abfd, char *buf, int *bufsiz, int note_ty
 
     case NT_PRPSINFO:
       {
-	char data[136];
+	char data[136] ATTRIBUTE_NONSTRING;
 	va_list ap;
 
 	va_start (ap, note_type);
diff --git a/bfd/peXXigen.c b/bfd/peXXigen.c
index 32ce195a00..a62d126aff 100644
--- a/bfd/peXXigen.c
+++ b/bfd/peXXigen.c
@@ -1051,9 +1051,10 @@  _bfd_XXi_swap_scnhdr_out (bfd * abfd, void * in, void * out)
        by ld --omagic, or by obcopy --writable-text.  */
 
     for (p = known_sections; p->section_name; p++)
-      if (strcmp (scnhdr_int->s_name, p->section_name) == 0)
+      if (strncmp (scnhdr_int->s_name, p->section_name,
+		   sizeof scnhdr_int->s_name) == 0)
 	{
-	  if (strcmp (scnhdr_int->s_name, ".text")
+	  if (strncmp (scnhdr_int->s_name, ".text", sizeof scnhdr_int->s_name)
 	      || (bfd_get_file_flags (abfd) & WP_TEXT))
 	    scnhdr_int->s_flags &= ~IMAGE_SCN_MEM_WRITE;
 	  scnhdr_int->s_flags |= p->must_have;
@@ -1066,7 +1067,7 @@  _bfd_XXi_swap_scnhdr_out (bfd * abfd, void * in, void * out)
   if (coff_data (abfd)->link_info
       && ! bfd_link_relocatable (coff_data (abfd)->link_info)
       && ! bfd_link_pic (coff_data (abfd)->link_info)
-      && strcmp (scnhdr_int->s_name, ".text") == 0)
+      && strncmp (scnhdr_int->s_name, ".text", sizeof scnhdr_int->s_name) == 0)
     {
       /* By inference from looking at MS output, the 32 bit field
 	 which is the combination of the number_of_relocs and
diff --git a/gas/config/obj-evax.c b/gas/config/obj-evax.c
index 642025f2ff..07a7067ebd 100644
--- a/gas/config/obj-evax.c
+++ b/gas/config/obj-evax.c
@@ -470,13 +470,13 @@  shorten_identifier (char *name)
   newname [MAX_LABEL_LENGTH] = 0;
   /* Now append the suffix of the original identifier, if any.  */
   if (suffix_length)
-  strncpy (newname + MAX_LABEL_LENGTH - suffix_length,
-	   name + len - suffix_length,
-	   suffix_length);
-  strncpy (newname + final_len, "_h", 2);
-  strncpy (newname + final_len + 2 , crc_chars, 5);
-  strncpy (newname + final_len + 2 + 5, encode_16 (len), 3);
-  strncpy (newname + final_len + 2 + 5 + 3, encode_16 (sum), 3);
+    strncpy (newname + MAX_LABEL_LENGTH - suffix_length,
+	     name + len - suffix_length,
+	     suffix_length);
+  memcpy (newname + final_len, "_h", 2);
+  memcpy (newname + final_len + 2 , crc_chars, 5);
+  memcpy (newname + final_len + 2 + 5, encode_16 (len), 3);
+  memcpy (newname + final_len + 2 + 5 + 3, encode_16 (sum), 3);
   if (!is_truncated_identifier (newname))
     abort ();
   return newname;
diff --git a/gas/config/obj-macho.c b/gas/config/obj-macho.c
index 4911907c9b..3ee98b9e5a 100644
--- a/gas/config/obj-macho.c
+++ b/gas/config/obj-macho.c
@@ -250,8 +250,10 @@  obj_mach_o_make_or_get_sect (char * segname, char * sectname,
 		 bfd_section_name (stdoutput, sec),
 		 bfd_errmsg (bfd_get_error ()));
 
-      strncpy (msect->segname, segname, sizeof (msect->segname));
-      strncpy (msect->sectname, sectname, sizeof (msect->sectname));
+      strncpy (msect->segname, segname, BFD_MACH_O_SEGNAME_SIZE);
+      msect->segname[BFD_MACH_O_SEGNAME_SIZE] = 0;
+      strncpy (msect->sectname, sectname, BFD_MACH_O_SECTNAME_SIZE);
+      msect->sectname[BFD_MACH_O_SECTNAME_SIZE] = 0;
 
       msect->align = secalign;
       msect->flags = sectype | secattr;
diff --git a/include/ansidecl.h b/include/ansidecl.h
index c11daffedb..406473ca9e 100644
--- a/include/ansidecl.h
+++ b/include/ansidecl.h
@@ -283,6 +283,15 @@  So instead we use the macro below and test it against specific values.  */
 # endif /* GNUC >= 4.9 */
 #endif /* ATTRIBUTE_NO_SANITIZE_UNDEFINED */
 
+/* Attribute 'nonstring' was valid as of gcc 8.  */
+#ifndef ATTRIBUTE_NONSTRING
+# if GCC_VERSION >= 8000
+#  define ATTRIBUTE_NONSTRING __attribute__ ((__nonstring__))
+# else
+#  define ATTRIBUTE_NONSTRING
+# endif
+#endif
+
 /* We use __extension__ in some places to suppress -pedantic warnings
    about GCC extensions.  This feature didn't work properly before
    gcc 2.8.  */
diff --git a/include/coff/internal.h b/include/coff/internal.h
index 1879ddc0a0..a8efedb7c4 100644
--- a/include/coff/internal.h
+++ b/include/coff/internal.h
@@ -393,7 +393,7 @@  struct internal_aouthdr
 
 struct internal_scnhdr
 {
-  char s_name[SCNNMLEN];	/* section name			*/
+  char s_name[SCNNMLEN] ATTRIBUTE_NONSTRING;	/* section name	*/
 
   /* Physical address, aliased s_nlib.
      In the pei format, this field is the virtual section size
@@ -466,7 +466,7 @@  struct internal_syment
 {
   union
   {
-    char _n_name[SYMNMLEN];	/* old COFF version		*/
+    char _n_name[SYMNMLEN] ATTRIBUTE_NONSTRING;	/* old COFF version	*/
     struct
     {
       bfd_hostptr_t _n_zeroes;	/* new == 0			*/