Add a FREE_AND_NULL() wrapper marco for the common pattern of freeing
a pointer and assigning NULL to it right afterwards.
The implementation is similar to the (currently unused) XDL_PTRFREE
macro in xdiff/xmacros.h added in commit 3443546f6e ("Use a *real*
built-in diff generator", 2006-03-24). The only difference is that
free() is called unconditionally, see [1].
See [2] for a suggested alternative which does this via a function
instead of a macro. As covered in replies to that message, while it's
a viable approach, it would introduce caveats which this approach
doesn't have, so that potential change is left to a future follow-up
change.
This merely allows us to translate exactly what we're doing now to a
less verbose & idiomatic form using a macro, while guaranteeing that
we don't introduce any functional changes.
1. <alpine.DEB.2.20.1608301948310.129229@virtualbox>
(http://public-inbox.org/git/alpine.DEB.2.20.1608301948310.129229@virtualbox/)
2. <20170610032143.GA7880@starla>
(https://public-inbox.org/git/20170610032143.GA7880@starla/)
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
git-compat-util.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/git-compat-util.h b/git-compat-util.h
index 51ba4e6b3b..047172d173 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -808,6 +808,12 @@ extern char *xgetcwd(void);
extern FILE *fopen_for_writing(const char *path);
extern FILE *fopen_or_warn(const char *path, const char *mode);
+/*
+ * FREE_AND_NULL(ptr) is like free(ptr) followed by ptr = NULL. Note
+ * that ptr is used twice, so don't pass e.g. ptr++.
+ */
+#define FREE_AND_NULL(p) do { free(p); (p) = NULL; } while (0)
+
#define ALLOC_ARRAY(x, alloc) (x) = xmalloc(st_mult(sizeof(*(x)), (alloc)))
#define REALLOC_ARRAY(x, alloc) (x) = xrealloc((x), st_mult(sizeof(*(x)), (alloc)))
--
2.13.1.508.gb3defc5cc