https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56670
Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |manu at gcc dot gnu.org
--- Comment #4 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Rich Townsend from comment #0)
> ...causes the following bogus warning:
If you compile with -fdump-tree-all-all-lineno and look at test.f90.004t.gimple
you'll see that gfortran generates:
[test.f90:5:0] name_formatD.3382 = 0B;
[test.f90:7:0] {
integer(kind=4)D.8 D.3383;
[test.f90:7:0] if (name_formatD.3382 != 0B) goto L.1D.3384; else goto
<D.3391>;
...
L.1D.3384:
[test.f90:7:0] if (.name_formatD.3381 == 0) goto L.2D.3385; else goto
<D.3392>;
If the last line is reached, then .name_format is used uninitialized. This
cannot happen here, because the first 'if' is always false. However, GCC does
not know that without the analysis done when using optimization. With -O1 there
is no warning.
(That code is quite strange, why test for != 0B after initializing it to 0B?)
> uninit_test.f90: In function ‘uninit_test’:
> uninit_test.f90:7:0: warning: ‘.name_format’ may be used uninitialized in
> this function [-Wmaybe-uninitialized]
> name_format = ''
> ^
>
> (Note also that the warning arises in the main program, and not in a
> function as the message suggests).
This is the output in a modern gfortran (with colors!):
test.f90:7:0:
name_format = ''
^
Warning: ‘.name_format’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
