https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102692
Bug ID: 102692
Summary: -Wanalyzer-null-dereference false alarm with (!p || q
|| !p->next)
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: analyzer
Assignee: dmalcolm at gcc dot gnu.org
Reporter: eggert at cs dot ucla.edu
Target Milestone: ---
Created attachment 51588
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51588&action=edit
compile on x86-64 with "gcc -fanalyzer -O2 -S
analyzer-null-dereference-simple.i"
I ran into this problem when compiling GNU Emacs with gcc 11.2.1 20210728 (Red
Hat 11.2.1-1) on x86-64. Compile the attached simplified version with:
gcc -fanalyzer -O2 -S analyzer-null-dereference-simple.i
and the output will be as at the end of this description. This output is bogus
since it complains that 'tail' might be null in (!tail || end < prev ||
!tail->next) which means that tail->next might dereference a null pointer. But
the tail->next expression is obviously unreachable if 'tail' is null.
Although this bug might be related to GCC bug 102671, I'm filing it separately
as it has a different feel.
