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* [Bug fortran/47307] New: be used uninitialized in this function
@ 2011-01-15 16:12 jszhao at yeah dot net
2011-01-15 16:42 ` [Bug middle-end/47307] Uninitialized in this function: warning for initialized, no warning for uninitialized burnus at gcc dot gnu.org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: jszhao at yeah dot net @ 2011-01-15 16:12 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47307
Summary: be used uninitialized in this function
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: jszhao@yeah.net
Hi there,
With the example code below, gfortran (4.5.0 and 4.6.0) give a strange warning
message with -O2 flag:
> gfortran -Wall -O2 -c readmo.f90
readmo.f90: In function 'readmo':
readmo.f90:4:0: warning: 'convrt' may be used uninitialized in this function
When with -O0, the warning message disappear.
In fact, the array 'lopt' is not initialized in the code, however, the compiler
does not give warning about that. I try the same code with g95, it give a
warning message 'used but not set' about 'lopt'.
Any suggestions or comments? Thanks in advance!
Regards,
Jinsong
subroutine readmo()
!!!! example code readmo.f90 !!!!
implicit none
real :: convrt
integer :: i, iflag, j
integer, dimension(3,5) :: lopt
iflag = 0
do i = 1, 5
do j = 1, 3
if ( lopt(j,i) < 0 ) then
convrt = 1.0
if ( j > 1 ) convrt = 2.0
iflag = 1
endif
enddo
enddo
if ( iflag /= 0 ) then
do i = 1, 5
write(6,*) i*convrt
enddo
endif
end subroutine readmo
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/47307] Uninitialized in this function: warning for initialized, no warning for uninitialized
2011-01-15 16:12 [Bug fortran/47307] New: be used uninitialized in this function jszhao at yeah dot net
@ 2011-01-15 16:42 ` burnus at gcc dot gnu.org
2011-01-15 22:26 ` dominiq at lps dot ens.fr
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: burnus at gcc dot gnu.org @ 2011-01-15 16:42 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47307
Tobias Burnus <burnus at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |diagnostic
CC| |burnus at gcc dot gnu.org
Component|fortran |middle-end
Summary|be used uninitialized in |Uninitialized in this
|this function |function: warning for
| |initialized, no warning for
| |uninitialized
--- Comment #1 from Tobias Burnus <burnus at gcc dot gnu.org> 2011-01-15 16:22:27 UTC ---
Move to middle end. From the dump:
readmo ()
{
integer(kind=4) lopt[15];
real(kind=4) convrt;
[...]
iflag = 0;
[...]
if (lopt[((integer(kind=8)) j + (integer(kind=8)) i * 3) + -4] < 0)
{
convrt = 1.0e+0;
iflag = 1;
}
if (iflag != 0)
... access convrt ...
Thus, lopt is never set, but not warned for. But convrt is only accessed if it
is set. However, the middle-end (with optimization) only has
warning: 'convrt' may be used uninitialized in this function
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/47307] Uninitialized in this function: warning for initialized, no warning for uninitialized
2011-01-15 16:12 [Bug fortran/47307] New: be used uninitialized in this function jszhao at yeah dot net
2011-01-15 16:42 ` [Bug middle-end/47307] Uninitialized in this function: warning for initialized, no warning for uninitialized burnus at gcc dot gnu.org
@ 2011-01-15 22:26 ` dominiq at lps dot ens.fr
2021-04-09 18:10 ` msebor at gcc dot gnu.org
2022-08-29 13:31 ` rguenth at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: dominiq at lps dot ens.fr @ 2011-01-15 22:26 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47307
--- Comment #2 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2011-01-15 21:50:05 UTC ---
> In fact, the array 'lopt' is not initialized in the code, however, the compiler
> does not give warning about that. I try the same code with g95, it give a
> warning message 'used but not set' about 'lopt'.
Add lopt(1,1) = 0 at the beginning of your code and the g95 warning just
disappears!
So don't rely too much of this kind of warning.
> Any suggestions or comments? Thanks in advance!
Searching bugzilla for "uninitialized" in the subject yields 52 entries for
open pr (not counting those closed as INVALID, DUPLICATE, WONTFIX, ...). I let
you browse the list to check if this pr is a duplicate of one of those (look
for instance to pr24639, my choice is pr27120).
As far as I understand the problem,
(1) it could be as difficult to solve as running the code itself (think of an
array of 10**9 elements set through a spaghetti code and forgetting to set only
one element). Note this apply also to duplicate initialization (as in Fortran
legalese;-).
(2) the responsibility to use only set variables is on the user, not on the
compiler.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/47307] Uninitialized in this function: warning for initialized, no warning for uninitialized
2011-01-15 16:12 [Bug fortran/47307] New: be used uninitialized in this function jszhao at yeah dot net
2011-01-15 16:42 ` [Bug middle-end/47307] Uninitialized in this function: warning for initialized, no warning for uninitialized burnus at gcc dot gnu.org
2011-01-15 22:26 ` dominiq at lps dot ens.fr
@ 2021-04-09 18:10 ` msebor at gcc dot gnu.org
2022-08-29 13:31 ` rguenth at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: msebor at gcc dot gnu.org @ 2021-04-09 18:10 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47307
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed|2017-12-30 00:00:00 |2021-4-9
CC| |msebor at gcc dot gnu.org
--- Comment #6 from Martin Sebor <msebor at gcc dot gnu.org> ---
The warning has disappeared at -O1 and above. The expected one for the
uninitialized read from the lopt array is issued now but only at -O0. With
optimization the read is eliminated. Given the large number of open bugs for
-Wuninitialized (pr24639) I'm not sure it's worth keeping this open as well.
$ gcc -O0 -S -Wall pr47307.f90
../pr47307.f90:13:13:
13 | if ( lopt(j,i) < 0 ) then
| ^
Warning: ‘lopt’ may be used uninitialized [-Wmaybe-uninitialized]
../pr47307.f90:8:34:
8 | integer, dimension(3,5) :: lopt
| ^
note: ‘lopt’ declared here
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/47307] Uninitialized in this function: warning for initialized, no warning for uninitialized
2011-01-15 16:12 [Bug fortran/47307] New: be used uninitialized in this function jszhao at yeah dot net
` (2 preceding siblings ...)
2021-04-09 18:10 ` msebor at gcc dot gnu.org
@ 2022-08-29 13:31 ` rguenth at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-08-29 13:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47307
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|NEW |RESOLVED
--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
The convrt thing is now working, the lopt diagnostic is given at -O0, the read
is indeed eliminated with optimization.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-08-29 13:31 UTC | newest]
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-- links below jump to the message on this page --
2011-01-15 16:12 [Bug fortran/47307] New: be used uninitialized in this function jszhao at yeah dot net
2011-01-15 16:42 ` [Bug middle-end/47307] Uninitialized in this function: warning for initialized, no warning for uninitialized burnus at gcc dot gnu.org
2011-01-15 22:26 ` dominiq at lps dot ens.fr
2021-04-09 18:10 ` msebor at gcc dot gnu.org
2022-08-29 13:31 ` rguenth at gcc dot gnu.org
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