https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89192
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |diagnostic Blocks| |24639 --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- It works with optimization: > g++-8 t.C -Wuninitialized -Wmaybe-uninitialized -O t.C: In function ‘int main()’: t.C:7:34: warning: ‘m.MyStruct::b’ is used uninitialized in this function [-Wuninitialized] MyStruct(unsigned arg1): vec(b), b(arg1){} ^ the reason is that at -O0 all calls such as the constructor are left in place and thus the uninitialized use is not exposed to function-local analysis. Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24639 [Bug 24639] [meta-bug] bug to track all Wuninitialized issues