OpenMP realloc lhs failure

[Ulrich_M_]

The following code, built with 19.1.2.254 in debug mode with "/standard-semantics" fails execution with "Critical error detected c0000374":

program mfort
	implicit none
	real, allocatable	:: x(:)
	integer		:: i,j
	
	x=[1,2,3] 
!$omp parallel do private(x)	
	do i=1,10
		x=[(j,j=1,12)]
		print *,sum(x)
	enddo
end program

[jimdempseyatthecove]

Try firstprivate(x)

so as to copy in the initial contents of the unallocated array descriptor.

Jim Dempsey

[Ulrich_M_]

Thank you for your suggestion.

In my real code, I had a function return a matrix of variable size. I tried a number of things there, including firstprivate, make the allocatable variables threadprivate with copyin, etc, but they all failed. In the end, I found a workaround by replacing the function by a subroutine that explicitly allocates the (initially deallocated) variable, and by deallocating the variable at the end of each loop iteration.

My conclusion is that the combination of OpenMP and automatic lhs reallocation is currently poorly implemented. The code above is merely a trivial reproducer.

[Ron_Green · Accepted solution]

Should be legal per spec Section 2.19.3

I'll open a bug report.

[Ron_Green]

you are correct - the seg fault is on deallocation after the loop exit.  the prints never get out of the stdout buffer before the seg fault hits.

[Ulrich_M_]

Thank you for taking a look!

UM

[Ron_Green]

Bug ID is CMPLRLLVM-23023