Add tests for deallocation bug, and a workaround

[certik]

The workaround leaks memory, so I think we should not commit this, and rather implement a proper fix.

[certik]

I think the dftatom fails because we are leaking to much memory and run out of memory.

[certik]

This PR allows me to compile and run stdlib without any segfaults. There are two tests added, but only one enabled for LFortran, and it tests the issue I had with stdlib.

In order to release the blog post, we need stdlib to work on all platforms, and this PR is one way to achieve it.

An alternative is to figure out a workaround in the Fortran source code of stdlib, but I wasn't able to figure out how to avoid it.

The second alternative is to wait until we have a proper fix for strings, which @Shaikh-Ubaid is working on, but that might take a while.

So I think it's fine to merge this PR, release stdlib blog post, and then work on a proper fix for strings.

@Shaikh-Ubaid, @Pranavchiku, @czgdp1807, let me know what you think.

[Shaikh-Ubaid]

It seems fine to me.

[Pranavchiku]

Can you try this diff,

diff --git a/subprojects/test-drive/src/testdrive.F90 b/subprojects/test-drive/src/testdrive.F90
index 1332be3..420d35f 100644
--- a/subprojects/test-drive/src/testdrive.F90
+++ b/subprojects/test-drive/src/testdrive.F90
@@ -405,6 +405,7 @@ contains
     !$omp critical(testdrive_testsuite)
     write(unit, '(a)') message
     !$omp end critical(testdrive_testsuite)
+    allocate(error)
     if (allocated(error)) then
       call clear_error(error)
     end if

[Pranavchiku]

Fine with me as well, we can go ahead and release blog.

[Pranavchiku]

Works for now, releasing blog is fine with me considering the failure not in Linux, latest macOS versions.

[certik]

@Pranavchiku I tried applying the following patch to this PR:

$ git diff bug4
diff --git a/integration_tests/dealloc_01.f90 b/integration_tests/dealloc_01.f90
index ebf759fcd..a9dad9ff4 100644
--- a/integration_tests/dealloc_01.f90
+++ b/integration_tests/dealloc_01.f90
@@ -72,6 +72,7 @@ contains
     end if
     call make_output(message, test_var, error)
     write(unit, '(a)') message
+    allocate(error)
   end subroutine run_unittest
 
   pure function test_skipped(error) result(is_skipped)
diff --git a/src/libasr/runtime/lfortran_intrinsics.c b/src/libasr/runtime/lfortran_intrinsics.c
index 9257dec49..bf69bc55a 100644
--- a/src/libasr/runtime/lfortran_intrinsics.c
+++ b/src/libasr/runtime/lfortran_intrinsics.c
@@ -1407,9 +1407,7 @@ LFORTRAN_API void _lfortran_strcpy(char** x, char *y, int8_t free_target)
 {
     if (free_target) {
         if (*x) {
-            // We should free `x` here, but cannot due to:
-            // https://github.com/lfortran/lfortran/issues/3787
-            //free((void *)*x);
+            free((void *)*x);
         }
         *x = (char*) malloc((strlen(y) + 1) * sizeof(char));
         _lfortran_string_init(strlen(y) + 1, *x);

But the error is still there.

[certik]

I merged it. The workaround is simple to revert, but let's see if we can release the stdlib blog post now.