xdiff/xprepare: fix a memory leak

The xdl_prepare_env() function may initialise an xdlclassifier_t data structure via xdl_init_classifier(), which allocates memory to several fields, for example 'rchash', 'rcrecs' and 'ncha'. If this function later exits due to the failure of xdl_optimize_ctxs(), then this xdlclassifier_t structure, and the memory allocated to it, is not cleaned up.

In order to fix the memory leak, insert a call to xdl_free_classifier() before returning.

Signed-off-by Ramsay Jones <[email protected]>

---
 xdiff/xprepare.c | 1 +
 1 file changed, 1 insertion(+)

xdiff/xprepare.c +0 -0

index 5ffcf99..13b55ab 100644

Quoted 20 lines · Ramsay Jones

The xdl_prepare_env() function may initialise an xdlclassifier_t data structure via xdl_init_classifier(), which allocates memory to several fields, for example 'rchash', 'rcrecs' and 'ncha'. If this function later exits due to the failure of xdl_optimize_ctxs(), then this xdlclassifier_t structure, and the memory allocated to it, is not cleaned up.

In order to fix the memory leak, insert a call to xdl_free_classifier() before returning.

Signed-off-by Ramsay Jones <[email protected]>

---
 xdiff/xprepare.c | 1 +
 1 file changed, 1 insertion(+)

xdiff/xprepare.c +0 -0

index 5ffcf99..13b55ab 100644

xdiff/xprepare.c int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, · line 306

Quoted 6 lines

xdiff/xprepare.c +1 -0

@@ -301,6 +301,7 @@ int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
 
 		xdl_free_ctx(&xe->xdf2);
 		xdl_free_ctx(&xe->xdf1);
+		xdl_free_classifier(&cf);
 		return -1;
 	}

This looks obviously correct from the pattern of prepare's and free's in the code that this part follows. This potential leak has been that way since 3443546f (Use a *real* built-in diff generator, 2006-03-24), i.e. the very beginning.

I find it somewhat strange that the call to xdl_free_classifier() at the end of this function is made conditional to XDF_HISTOGRAM_DIFF, though. I can half-buy the argument "that is because we do not call init-classifier for XDF_HISTOGRAM_DIFF", but in the error path we call free-classifier unconditionally, so the code clearly knows that it is safe to call free-classifier on a classifier that is cleared with the initial memset(&cf, 0, sizeof cf).