Setting LG_init_has_been_called = false after LAGraph_finalize

[jamesETsmith]

General

I recently came across a problem where LG_init_has_been_called (defined as a global variable in src/utility/LAGr_init.c) isn't set to false in between subtests in test_BreadthFirstSearch which triggers a cascade of problems which were somewhat tough to track down.

I can only reproduce this error with a modified version of clang 6.0.0 where LAGraph is built with LAGRAPH_VANILLA=1 and linked to Lucata's implementation of GraphBLAS).

Details

This is somewhat convoluted to describe so please ask questions if the following isn't clear. When LAGr_init() fails, it calls GrB_finalize, but since the error in LAGraph_Init() isn't caught inside setup() (see here), the subtest proceeds. It will then try to call GrB_finalize() again (if it doesn't crash earlier) which leads to freeing already freed memory.

Proposed Solution

• Primary Change: add extern bool LG_init_has_been_called; to LAGraph_Finalize.c and set it to false when LAGraph_Finalize() completes successfully
• Minor change: Wrap LAGraph_Init and LAGraph_Finalize in checks to make sure the user knows if they fail.

I'm happy to open a PR with these changes, but I wanted to discuss them first. Let me know what you think.

[DrTimothyAldenDavis]

I talked this over with the LAGraph group. We have a different proposed solution.

First of all, I moved the setting of this flag (now called LG_LAGr_Init_has_been_called) to occur at the very end of LAGr_init. This will help in the rare but possible user situation where LAGr_Init fails.

I also added two functions to set/get this flag (see LAGr_Init.c in the v1.1_branch). In normal usage, the flag should only be set by LAGr_Init. It should not be cleared by LAGraph_Finalize, as you suggest, however.

But what you can do is what we have in test_Xinit. That method adds the prototypes of these two set/get functions, so it can clear and set the flag as needed for its tests. In particular, the test_Xinit_brutal method tests LAGr_Init many times, all with pretend failures of running out of memory, and successfully recovers.

LAGraph_Finalize can safely free any partially allocated blocks of memory that were allocated by LAGr_Init.

So if you'd like control over this flag in your tests, just add the prototypes to your tests:

LAGRAPH_PUBLIC void LG_set_LAGr_Init_has_been_called (bool setting) ;
LAGRAPH_PUBLIC bool LG_get_LAGr_Init_has_been_called (void) ;