DragonFlyBSD

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.