Date: Tue, 10 Feb 2004 10:09:03 +0100 From: des@des.no (Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?=) To: hackers@freebsd.org Subject: how to fool gcc? Message-ID: <xzpad3r5mj4.fsf@dwp.des.no>
next in thread | raw e-mail | index | archive | help
I'm having trouble with some uncommitted OpenPAM patches that I'd like
to get into the tree. The problem actually doesn't occur with a
normal build, but it prevents me from building a debugging version of
libpam.
Part of the patch declares openpam_log(3) as printf-like so gcc can
check format strings etc. However, openpam_log(3) is also used in
debugging macros such as this:
#define RETURNS(s) do { \
if ((s) =3D=3D NULL) \
openpam_log(PAM_LOG_DEBUG, "returning NULL"); \
else \
openpam_log(PAM_LOG_DEBUG, "returning '%s'", (s)); \
return (s); \
} while (0)
The problem is that when it encounters RETURNS(NULL), gcc complains
that I'm passing a NULL argument to printf(3), even though it should
be obvious that I'm not:
cc -O -pipe -march=3Dpentium2 -I/usr/src/lib/libpam/libpam -I/home/des/proj=
ects/openpam/include -DLIB_MAJ=3D2 -g -DDEBUG -Wsystem-headers -Werror -Wal=
l -Wno-format-y2k -W -Wstrict-prototypes -Wmissing-prototypes -Wpointer-ari=
th -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wshadow -Wcast-align=
-Wbad-function-cast -Wchar-subscripts -Winline -Wnested-externs -Wredundan=
t-decls -c /home/des/projects/openpam/lib/openpam_get_option.c
/home/des/projects/openpam/lib/openpam_get_option.c: In function `openpam_g=
et_option':
/home/des/projects/openpam/lib/openpam_get_option.c:62: warning: reading th=
rough null pointer (arg 4)
/home/des/projects/openpam/lib/openpam_get_option.c:73: warning: reading th=
rough null pointer (arg 4)
*** Error code 1
Stop in /usr/src/lib/libpam/libpam.
I've tried various twists to fool gcc, such as casting (s) to (const
char *) and adding 0 to it hoping that the addition would defeat its
NULL pointer check. Nothing I've tried works, though, and I would
really hate to have to lower the WANRS level just for this.
Any suggestions?
DES
--=20
Dag-Erling Sm=F8rgrav - des@des.no
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?xzpad3r5mj4.fsf>