On 08/07/2022 15:20, Ævar Arnfjörð Bjarmason wrote:
As noted in 36c83197249 (xdiff: use xmalloc/xrealloc, 2019-04-11) the
reason we have xdl_malloc() in the first place was to make the xdiff
code safer, it was not handling some allocation failures correctly at
the time.
This is untrue, we do not have xdl_malloc to make the xdiff code safer,
that macro was introduced with the initial import of xdiff. 36c83197249
just changed its definition, the entire commit consists of
-#define xdl_malloc(x) malloc(x)
+#define xdl_malloc(x) xmalloc(x)
#define xdl_free(ptr) free(ptr)
-#define xdl_realloc(ptr,x) realloc(ptr,x)
+#define xdl_realloc(ptr,x) xrealloc(ptr,x)
I can see the argument for reverting that change now that we have fixed
the error checking but that is not a good reason to remove xdl_malloc().
Best Wishes
Phillip
But as noted in that commit doing this was intended as a stopgap, as
various code in xdiff/* did not correctly handle allocation failures,
and would have segfaulted if malloc() returned NULL.
But since then and after preceding commits we can be confident that
malloc() failures are handled correctly. All of these users of
xdl_malloc() are checking their return values, and we're returning
-1 (or similar ) to the top-level in case of failures.
This also has the big advantage of making the compiler and analysis
tools less confused, and potentially avoiding undefined (compiler)
behavior. I.e. we define our own xmalloc() to call die() on failure,
and that function uses the non-standard "noreturn" attribute on our
most common compiler targets.
But xdl_malloc()'s use conflicted with that, confusing both human
readers of this code, and potentially compilers as well.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
xdiff/xdiff.h | 1 -
xdiff/xdiffi.c | 2 +-
xdiff/xmerge.c | 10 +++++-----
xdiff/xutils.c | 2 +-
4 files changed, 7 insertions(+), 8 deletions(-)
diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index 832cf9d977e..df048e0099b 100644
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -119,7 +119,6 @@ typedef struct s_bdiffparam {
} bdiffparam_t;
-#define xdl_malloc(x) xmalloc(x)
#define xdl_free(ptr) free(ptr)
void *xdl_mmfile_first(mmfile_t *mmf, long *size);
diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
index 077cc456087..6590811634f 100644
--- a/xdiff/xdiffi.c
+++ b/xdiff/xdiffi.c
@@ -368,7 +368,7 @@ int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2) {
xdchange_t *xch;
- if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t))))
+ if (!(xch = (xdchange_t *) malloc(sizeof(xdchange_t))))
return NULL;
xch->next = xscr;
diff --git a/xdiff/xmerge.c b/xdiff/xmerge.c
index ac0cf52f3be..676ad39020d 100644
--- a/xdiff/xmerge.c
+++ b/xdiff/xmerge.c
@@ -60,7 +60,7 @@ static int xdl_append_merge(xdmerge_t **merge, int mode,
m->chg1 = i1 + chg1 - m->i1;
m->chg2 = i2 + chg2 - m->i2;
} else {
- m = xdl_malloc(sizeof(xdmerge_t));
+ m = malloc(sizeof(xdmerge_t));
if (!m)
return -1;
m->next = NULL;
@@ -409,7 +409,7 @@ static int xdl_refine_conflicts(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m,
m->i2 = xscr->i2 + i2;
m->chg2 = xscr->chg2;
while (xscr->next) {
- xdmerge_t *m2 = xdl_malloc(sizeof(xdmerge_t));
+ xdmerge_t *m2 = malloc(sizeof(xdmerge_t));
if (!m2) {
xdl_free_env(&xe);
xdl_free_script(x);
@@ -670,7 +670,7 @@ static int xdl_do_merge(xdfenv_t *xe1, xdchange_t *xscr1,
ancestor_name,
favor, changes, NULL, style,
marker_size);
- result->ptr = xdl_malloc(size);
+ result->ptr = malloc(size);
if (!result->ptr) {
xdl_cleanup_merge(changes);
return -1;
@@ -718,14 +718,14 @@ int xdl_merge(mmfile_t *orig, mmfile_t *mf1, mmfile_t *mf2,
}
status = 0;
if (!xscr1) {
- result->ptr = xdl_malloc(mf2->size);
+ result->ptr = malloc(mf2->size);
if (!result->ptr)
goto out;
status = 0;
memcpy(result->ptr, mf2->ptr, mf2->size);
result->size = mf2->size;
} else if (!xscr2) {
- result->ptr = xdl_malloc(mf1->size);
+ result->ptr = malloc(mf1->size);
if (!result->ptr)
goto out;
status = 0;
diff --git a/xdiff/xutils.c b/xdiff/xutils.c
index c0cd5338c4e..865e08f0e93 100644
--- a/xdiff/xutils.c
+++ b/xdiff/xutils.c
@@ -98,7 +98,7 @@ void *xdl_cha_alloc(chastore_t *cha) {
void *data;
if (!(ancur = cha->ancur) || ancur->icurr == cha->nsize) {
- if (!(ancur = (chanode_t *) xdl_malloc(sizeof(chanode_t) + cha->nsize))) {
+ if (!(ancur = (chanode_t *) malloc(sizeof(chanode_t) + cha->nsize))) {
return NULL;
}
