#193 New -Wrestrict warning with GCC9

[Martin Liška]

Using latest GCC, one can see:

$ /bin/sh ../libtool  --tag=CC   --mode=compile gcc -DHAVE_CONFIG_H -I. -I..  -I.. -I../autoopts  -DPKGDATADIR='"/usr/local/share/autogen"' -g -O2 -Wno-format-contains-nul -fno-strict-aliasing -Wall -Werror -Wcast-align -Wmissing-prototypes -Wpointer-arith -Wshadow -Wstrict-prototypes -Wwrite-strings -Wstrict-aliasing=3 -Wextra -Wno-cast-qual -g -O2 -Wno-format-contains-nul -fno-strict-aliasing -c -o libopts_la-libopts.lo `test -f 'libopts.c' || echo './'`libopts.c
libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I.. -I.. -I../autoopts -DPKGDATADIR=\"/usr/local/share/autogen\" -g -O2 -Wno-format-contains-nul -fno-strict-aliasing -Wall -Werror -Wcast-align -Wmissing-prototypes -Wpointer-arith -Wshadow -Wstrict-prototypes -Wwrite-strings -Wstrict-aliasing=3 -Wextra -Wno-cast-qual -g -O2 -Wno-format-contains-nul -fno-strict-aliasing -c libopts.c  -fPIC -DPIC -o .libs/libopts_la-libopts.o
In file included from autoopts.c:42,
                 from libopts.c:22:
In function ‘canonicalize_pathname’,
    inlined from ‘option_pathfind.constprop’ at ../compat/pathfind.c:88:32:
../compat/pathfind.c:214:17: error: ‘strcpy’ accessing 1 byte at offsets [0, 9223372036854775807] and [0, 9223372036854775807] may overlap 1 byte at offset 0 [-Werror=restrict]
  214 |                 strcpy( result + start + 1, result + i + 2 );
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It's explained and analyzed here:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88973

[Bruce Korb]

I didn't write this code. The person who did is no longer able to help (employer restriction). I haven't been writing code for 5 years, so a patch would be welcome. :)

Otherwise, I'll take a gander when I get back from an out-of-country wedding this April.

[Martin Liška]

I can come up with a patch candidate.

[Martin Liška]

Patch candiate:

diff --git a/compat/pathfind.c b/compat/pathfind.c
index 5c477ca..6a4eeb5 100644
--- a/compat/pathfind.c
+++ b/compat/pathfind.c
@@ -136,6 +136,18 @@ make_absolute( char const * string, char const * dot_path )
     return result;
 }

+/*

+ * Proccess strcpy for overlapping memory locations.
+ */
+static char*
+strcpy_overlapping ( char *d, const char *s)
+{
+  unsigned n = strlen ( s );
+  memmove ( d, s, n + 1 );
+  return d;
+}
+
+
 /*
  * Canonicalize PATH, and return a  new path.  The new path differs from
  * PATH in that:
@@ -182,7 +194,7 @@ canonicalize_pathname( char *path )
         if ((start + 1) != i && (start != 0 || i != 2))
 #endif /* apollo */
         {
-            strcpy( result + start + 1, result + i );
+            strcpy_overlapping( result + start + 1, result + i );
             i = start + 1;
         }

@@ -201,7 +213,7 @@ canonicalize_pathname( char *path )
         if (result[i] == '.') {
             /* Handle `./'. */
             if (result[i + 1] == '/') {

-                strcpy( result + i, result + i + 1 );
+                strcpy_overlapping( result + i, result + i + 1 );
                 i = (start < 0) ? 0 : start;
                 continue;
             }
@@ -211,7 +223,7 @@ canonicalize_pathname( char *path )
                 (result[i + 2] == '/' || !result[i + 2])) {
                 while (--start > -1 && result[start] != '/')
                     ;
-                strcpy( result + start + 1, result + i + 2 );
+                strcpy_overlapping( result + start + 1, result + i + 2 );
                 i = (start < 0) ? 0 : start;
                 continue;
             }

[Martin Liška]

Any opinion about the patch? Thanks.

[Bruce Korb]

Looks good to me, but strcpy should have been a void procedure from the get-go.
Since we're fixing a warning triggered by a "we must warn about every
conceivable
issue", the return value from strcpy/strcpy_overlapping is ignored. May as well
make this warning-go-away fix be scrupulous, too:

static void
strcpy_overlapping(char d, const char s)
{
memmove(d, s, strlen(s) + 1);
}

I'll be back from a wedding the end of March.

On Tue, Feb 26, 2019 at 2:19 AM "Martin Liška"
marxin@users.sourceforge.net wrote:

Any opinion about the patch? Thanks.

---

[bugs:#193] New -Wrestrict warning with GCC9

Status: open
Group: autogen
Created: Tue Feb 19, 2019 09:34 AM UTC by Martin Liška
Last Updated: Wed Feb 20, 2019 11:52 AM UTC
Owner: nobody

Using latest GCC, one can see:

$ /bin/sh ../libtool --tag=CC --mode=compile gcc -DHAVE_CONFIG_H -I. -I.. -I.. -I../autoopts -DPKGDATADIR='"/usr/local/share/autogen"' -g -O2 -Wno-format-contains-nul -fno-strict-aliasing -Wall -Werror -Wcast-align -Wmissing-prototypes -Wpointer-arith -Wshadow -Wstrict-prototypes -Wwrite-strings -Wstrict-aliasing=3 -Wextra -Wno-cast-qual -g -O2 -Wno-format-contains-nul -fno-strict-aliasing -c -o libopts_la-libopts.lo test -f 'libopts.c' || echo './'libopts.c
libtool: compile: gcc -DHAVE_CONFIG_H -I. -I.. -I.. -I../autoopts -DPKGDATADIR=\"/usr/local/share/autogen\" -g -O2 -Wno-format-contains-nul -fno-strict-aliasing -Wall -Werror -Wcast-align -Wmissing-prototypes -Wpointer-arith -Wshadow -Wstrict-prototypes -Wwrite-strings -Wstrict-aliasing=3 -Wextra -Wno-cast-qual -g -O2 -Wno-format-contains-nul -fno-strict-aliasing -c libopts.c -fPIC -DPIC -o .libs/libopts_la-libopts.o
In file included from autoopts.c:42,
from libopts.c:22:
In function ‘canonicalize_pathname’,
inlined from ‘option_pathfind.constprop’ at ../compat/pathfind.c:88:32:
../compat/pathfind.c:214:17: error: ‘strcpy’ accessing 1 byte at offsets [0, 9223372036854775807] and [0, 9223372036854775807] may overlap 1 byte at offset 0 [-Werror=restrict]
214 | strcpy( result + start + 1, result + i + 2 );
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It's explained and analyzed here:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88973

---

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[Bruce Korb]

strcpy-s were replaced with memmove directly.
fixed.