https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82601
Bug ID: 82601
Summary: missing uninitialized warning with -O0 / -Og
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: janus at gcc dot gnu.org
Target Milestone: ---
Consider this simple Fortran test case:
program uninit
integer :: p,q
p = -1
call sub(p, q)
if (p<q) print *,"..."
contains
subroutine sub(i, o)
integer, intent(in) :: i
integer, intent(out) :: o
if (i<0) then
print *, "..."
else
o = 1
end if
end subroutine
end
With -Wall and -O1 (or higher), all recent gfortran versions print:
if (p<q) print *,"..."
Warning: ‘q’ is used uninitialized in this function [-Wuninitialized]
However, with -O0 or -Og, no warning is issued.
It should be possible to detect that 'o' may be uninitialized by looking only
at the subroutine itself (without any information about the caller).
