https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107289
Geoffrey <geoffreydgr at icloud dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |geoffreydgr at icloud dot com --- Comment #3 from Geoffrey <geoffreydgr at icloud dot com> --- (In reply to David Malcolm from comment #2) > I believe that the analyzer is considering the case where "d" is (somehow) > called from outside of "main", and thus not making the assumption that *b == > &a; seeing the compare with NULL, it considers the case that b could be NULL. > > It's not yet clear to me that this case of d being called from outside > "main" is valid, or if it's always the case that d can only ever be called > from main. In addition, i changed the original case to the following one (only add specifier static to `d`) and Compiled it with gcc 12.1 with `-O0 -fanalyzer` ``` int a=1; int *b = &a; void c () { int f; f = *b; } void e (){ if (0 == b){ int *g = 0; } } static void d() { e(); c(); } int main(){ d(); } ``` results in: ``` <source>: In function 'void c()': <source>:5:7: warning: dereference of NULL 'b' [CWE-476] [-Wanalyzer-null-dereference] 5 | f = *b; | ~~^~~~ 'void d()': events 1-2 | | 12 | static void d() { | | ^ | | | | | (1) entry to 'd' | 13 | e(); | | ~~~ | | | | | (2) calling 'e' from 'd' | +--> 'void e()': events 3-6 | | 7 | void e (){ | | ^ | | | | | (3) entry to 'e' | 8 | if (0 == b){ | | ~~ | | | | | (4) following 'true' branch... | 9 | int *g = 0; | | ~ | | | | | (5) ...to here | | (6) 'b' is NULL | <------+ | 'void d()': events 7-8 | | 13 | e(); | | ~^~ | | | | | (7) returning to 'd' from 'e' | 14 | c(); | | ~~~ | | | | | (8) calling 'c' from 'd' | +--> 'void c()': events 9-10 | | 3 | void c () { | | ^ | | | | | (9) entry to 'c' | 4 | int f; | 5 | f = *b; | | ~~~~~~ | | | | | (10) dereference of NULL 'b' | ``` Static analyzer should not give the CWE-476 warning, and it should start analyzing from function main instead of function `d` because function `d` is a static function (it is visible only in this compile unit) and only called by function `main`. And i am wondering how gcc analyzer handles global variables?