Bug #1711

memmem() in string.h should be more or less VISIBLE on x86_64?

Added by davshao about 4 years ago. Updated about 2 years ago.

Status:ClosedStart date:
Priority:NormalDue date:
Assignee:-% Done:

0%

Category:-
Target version:-

Description

The memmem() function has a prototype given in /usr/include/string.h, (and
/usr/src/lib/libc/string/memmem.c exists) only it is required that __BSD_VISIBLE
be defined. Unfortunately a check of gcc 4.1.2

gcc -E -dM - < /dev/null | sort

shows no sign of any *VISIBLE.

Suppose on x86_64 some package, say scmgit-base, detects the existence of
memmem() yet because it too does not define any *VISIBLE uses an implicit
definition of memmem(), as is indicated in the build messages:

checking for memmem... yes
checking for library containing memmem... none required
and

diff.c:369: warning: implicit declaration of function 'memmem'

From scmgit-base's configure it is just a simple test for memmem(), essentially just

char memmem ();
int
main ()
{
return memmem ();
;
return 0;
}

Then the return value of the actual memmem() that should be (void *) I believe
suddenly becomes an int, so that what used to be a valid pointer after the
return is now possibly not a valid pointer on x86_64 if it is truncated and then
sign extended to a negative 64-bit number. For example, using

git diff HEAD^ HEAD

produces segmentation fault errors.

So far setting
NO_MEMMEM = YesPlease
in git's entry for DragonFly in its Makefile does not appear to have solved the
problem.

History

#1 Updated by swildner about 4 years ago

Am 31.03.2010 21:55, schrieb David Shao (via DragonFly issue tracker):
>
> New submission from David Shao<>:
>
> The memmem() function has a prototype given in /usr/include/string.h, (and
> /usr/src/lib/libc/string/memmem.c exists) only it is required that __BSD_VISIBLE
> be defined. Unfortunately a check of gcc 4.1.2
>
> gcc -E -dM -< /dev/null | sort
>
> shows no sign of any *VISIBLE.

__BSD_VISIBLE is not a builtin. It's defined in <sys/cdefs.h> and is 1
for our default compilation environment (unless any _POSIX_C_SOURCE or
similar macros are set).

Sascha

#2 Updated by qhwt+dfly about 4 years ago

:
> Then the return value of the actual memmem() that should be (void *) I believe
> suddenly becomes an int, so that what used to be a valid pointer after the
> return is now possibly not a valid pointer on x86_64 if it is truncated and then
> sign extended to a negative 64-bit number. For example, using
>
> git diff HEAD^ HEAD
>
> produces segmentation fault errors.

This particular issue in git should have been solved in pkgsrc-HEAD,
can you try updating the devel/scmgit-base directory and re-install it?

Cheers.

#3 Updated by swildner about 2 years ago

  • Status changed from New to Closed
  • Assignee deleted (0)

All issues fixed, closing.

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