https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71157
Bug ID: 71157
Summary: -Wnull-dereference false alarm in wrong function
Product: gcc
Version: 6.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: eggert at gnu dot org
Target Milestone: ---
Created attachment 38504
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38504&action=edit
preprocessed source code for emacs/lib-src/etags.c
I discovered this when compiling bleeding-edge GNU Emacs with GCC 6.1.0 on
x86-64. For the attached file e.i, the shell command:
gcc -O2 -S -Wnull-dereference e.i
issues the diagnostics:
e.i: In function 'Forth_words':
e.i:9690:10: warning: potential null pointer dereference [-Wnull-dereference]
while (*cp != '\0' && !c_isspace (*cp))
^~~
e.i:9690:10: warning: potential null pointer dereference [-Wnull-dereference]
e.i:9690:10: warning: potential null pointer dereference [-Wnull-dereference]
I see three things wrong with these diagnostics. First, line 9690 is nowhere
near the function Forth_words. Second, I see no path to line 9690 in which its
pointer CP can possibly be null. Furthermore, CP is dereferenced only twice in
line 9690, so why are there three warnings?
