https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87043
Bug ID: 87043
Summary: maybe-uninitialized warning for initialized variable
Product: gcc
Version: 8.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: pvitt at posteo dot de
Target Milestone: ---
We have a MWE that provokes a "may be uninitialized" warning despite the value
being initialized in all cases. Additionally, this warning is only created with
-O[1,2,3,s,fast}, but not with -O{g}. The gcc is from Arch Linux.
$ gfortran -v -save-temps -O3 -Wmaybe-uninitialized uninitialized.f90
Driving: gfortran -v -save-temps -O3 -Wmaybe-uninitialized uninitialized.f90 -l
gfortran -l m -shared-libgcc
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/8.1.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib
--libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared
--enable-threads=posix --enable-libmpx --with-system-zlib --with-isl
--enable-__cxa_atexit --disable-libunwind-exceptions --enable-clocale=gnu
--disable-libstdcxx-pch --disable-libssp --enable-gnu-unique-object
--enable-linker-build-id --enable-lto --enable-plugin
--enable-install-libiberty --with-linker-hash-style=gnu
--enable-gnu-indirect-function --enable-multilib --disable-werror
--enable-checking=release --enable-default-pie --enable-default-ssp
Thread model: posix
gcc version 8.1.1 20180531 (GCC)
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-O3' '-Wmaybe-uninitialized'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'
/usr/lib/gcc/x86_64-pc-linux-gnu/8.1.1/f951 uninitialized.f90 -quiet -dumpbase
uninitialized.f90 -mtune=generic -march=x86-64 -auxbase uninitialized -O3
-Wmaybe-uninitialized -version -fintrinsic-modules-path
/usr/lib/gcc/x86_64-pc-linux-gnu/8.1.1/finclude -o uninitialized.s
GNU Fortran (GCC) version 8.1.1 20180531 (x86_64-pc-linux-gnu)
compiled by GNU C version 8.1.1 20180531, GMP version 6.1.2, MPFR
version 4.0.1, MPC version 1.1.0, isl version isl-0.19-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU Fortran2008 (GCC) version 8.1.1 20180531 (x86_64-pc-linux-gnu)
compiled by GNU C version 8.1.1 20180531, GMP version 6.1.2, MPFR
version 4.0.1, MPC version 1.1.0, isl version isl-0.19-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
uninitialized.f90:20:0:
max_err_len = maxval(len_trim(error_messages))
Warning: ‘error_messages.dim[0].ubound’ may be used uninitialized in this
function [-Wmaybe-uninitialized]
[stripped assembler output...]
$ cat uninitialized.f90
module m
implicit none
integer, parameter :: error_buflen = 80
integer :: world_rank, world_size
contains
subroutine test()
character(len=error_buflen), allocatable :: error_messages(:)
integer :: allocstat, max_err_len
max_err_len = 0
if (world_rank == 0 ) then
allocate(error_messages(world_size), stat=allocstat)
else
allocate(error_messages(0))
end if
if (world_rank == 0) then
max_err_len = maxval(len_trim(error_messages))
end if
if (max_err_len > error_buflen-10) then
write(*,'(a)') 'Note...'
end if
end subroutine test
end module
program uninitialized
use m
implicit none
read(*,*) world_rank
world_size = 2
call test()
end program
