[Bug fortran/100440] allocated() gives True for unallocated variable

["sgk at troutmask dot apl.washington.edu" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100440

--- Comment #3 from Steve Kargl <sgk at troutmask dot apl.washington.edu> ---
On Thu, May 06, 2021 at 09:31:49PM +0000, David.Smith at lmu dot edu wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100440
> 
> --- Comment #2 from David.Smith at lmu dot edu ---
> >  With neither access to the actual code nor a reduced testcase,
> >  it will be virtually impossible to debug this problem.
> 
> Right, I have enclosed a small program pulled out of my real application
> that displays the error.

Thanks for reduce this to a testcase.  I don't see it attached
to this email or in bugzilla.   gcc.gno.org may have stripped
the attachment (for some dumb reason).  Feel free to send the
test case to me, and I make sure it gets attached to the bug
report.

> 
> >  Does the code run with the following compiler options:
> 
> >  -O0 -fno-frontend-optimize -fcheck=all
> 
> Yes, it compiles and runs, giving the allocate error.
> 
> >  Does the code compile without warning if you use -Wall -Wextra?
> 
> There are many warnings, and I think they may all be ignored for this
> program:
> 
>     IUNKNO = -HUGE(I_TWO)/18
>     Warning: Integer division truncated to constant ‘119304647’
> 
>         (Yes, that is what we want)
> 
>     IF (MB%MP(2) /= MUNKNO .OR. MB%MP(3) /= 1) THEN
>     Warning: Inequality comparison for REAL(8)
> 
>         (This is a numerical analysis application -- it knows what it is
>          doing when it compares reals)
> 
>     KT1 = MWA%MP(J+1)
>     Warning: Possible change of value in conversion from REAL(8) to INTEGER(4)
> 
>         (ditto)
> 
>     TYPE(MULTI), SAVE, DIMENSION(LMBERN) :: MBERN
>     Warning: Array ‘mbern’ at (1) is larger than limit set by
> ‘-fmax-stack-var-size=’,
>     moved from stack to static storage.
> 
>         (That's fine here)
> 
>     INTEGER :: J,JMA,JMW,N1,N2
>     Warning: Unused variable ‘jma’ declared
> 
>         (I removed most of the routines in the full program to make a small
>          version that gives the error.  Also removed some test code that uses
>          these 'unused' variables)
> 
>    IF (KRESLT /= 0) THEN
>    Warning: ‘kreslt’ may be used uninitialized in this function
> 
>         (ditto)
> 
> 
> 
> I have attached the file "allocate_error.f95".  Output (without the warnings):
> 
> 
> gfortran allocate_error.f95 -o allocate_error  -Wall -Wextra  -O0
> -fno-frontend-optimize -fcheck=all
> $ allocate_error
> 
> 
> 
>  Sample 10.  Eigenvalue from matrix powers.
> 
>  Iteration    eigenvalue approximation
> 
>          0     1.000000000000000000000000000000000000000000000000000000000
>  21 j=           1  allocated(FMMATMUL21_FM(J)%MFM%mp) =  T
>   size(FMMATMUL21_FM(J)%MFM%mp) =            1
>  allocate_error(29813,0x108292dc0) malloc: *** error for object
> 0xb000000000000000: pointer being freed was not allocated
> allocate_error(29813,0x108292dc0) malloc: *** set a breakpoint in
> malloc_error_break to debug
> 
> Program received signal SIGABRT: Process abort signal.
> 
> Backtrace for this error:
> #0  0x104c1ad3d
> #1  0x104c1a16d
> #2  0x7fff6f56042c
> zsh: abort      allocate_error

The above malloc error suggests to me that you're 
possibly stepping off the end of an array.  -fcheck=all
should have caught that. :(