[Bug libgomp/81591] segmentation fault when using priorities of nested tasks

[sistek at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81591

--- Comment #5 from Jakub Sistek <sistek at seznam dot cz> ---
Created attachment 41879
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41879&action=edit
test case producing an error

Hello Jakub,

thanks for looking into it. I have been able to isolate our problem into the
attached simple C code.

It is compiled with:
CC       = ${HOME}/software/gcc/gcc_installed/bin/gcc
CFLAGS   = ${FPIC} -std=c99 -fopenmp -O3 -g
LIBS     = -L${HOME}/software/gcc/gcc_installed/lib64
-Wl,-rpath,${HOME}/software/gcc/gcc_installed/lib64

If run with:
OMP_NUM_THREADS=4 OMP_MAX_TASK_PRIORITY=0 ./nested_omp_tasks
it produces correct output. 
 Matrix after update:
    1     0     0     0 
    1     1     0     0 
    1     1     1     0 
    1     1     1     1 

When run with nonzero max priority, e.g. by
OMP_NUM_THREADS=4 OMP_MAX_TASK_PRIORITY=10 ./nested_omp_tasks 
it finishes with an error:
libgomp: priority_tree_next_task: t1 != t2

This error is enabled by the _LIBGOMP_CHECKING_. I was getting segfaults if the
checking is not enabled.

Thanks for investigating it!

Best wishes,

Jakub