[issue1711] memmem() in string.h should be more or less VISIBLE on x86_64?

David Shao (via DragonFly issue tracker) sinknull at leaf.dragonflybsd.org
Wed Mar 31 12:56:20 PDT 2010

New submission from David Shao <davshao at gmail.com>:

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
    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 ();
    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

keyword: pkgsrc, standards
messages: 8329
nosy: davshao
status: unread
title: memmem() in string.h should be more or less VISIBLE on x86_64?

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