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[Xen-devel] [PATCH 11/19] libxl: Make libxl__zalloc et al tolerate a NULL gc

Arrange that if we pass NULL as a gc, we simply don't register the
pointer.  This instantly gives us non-gc'ing but error-checking
versions of malloc, realloc, vasprintf, etc.

Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
 tools/libxl/libxl_internal.c |    5 ++++-
 tools/libxl/libxl_internal.h |   21 +++++++++++++--------
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/tools/libxl/libxl_internal.c b/tools/libxl/libxl_internal.c
index 4ed9412..b89aef7 100644
--- a/tools/libxl/libxl_internal.c
+++ b/tools/libxl/libxl_internal.c
@@ -34,6 +34,9 @@ void libxl__ptr_add(libxl__gc *gc, void *ptr)
     int i;
+    if (!gc)
+        return;
     if (!ptr)
@@ -101,7 +104,7 @@ void *libxl__realloc(libxl__gc *gc, void *ptr, size_t 
     if (ptr == NULL) {
         libxl__ptr_add(gc, new_ptr);
-    } else if (new_ptr != ptr) {
+    } else if (new_ptr != ptr && gc != NULL) {
         for (i = 0; i < gc->alloc_maxsize; i++) {
             if (gc->alloc_ptrs[i] == ptr) {
                 gc->alloc_ptrs[i] = new_ptr;
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 2ad446a..9340bde 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -384,30 +384,35 @@ static inline libxl_ctx *libxl__gc_owner(libxl__gc *gc)
  * All pointers returned by these functions are registered for garbage
  * collection on exit from the outermost libxl callframe.
+ *
+ * However, where the argument is stated to be "gc_opt", NULL may be
+ * passed instead, in which case no garbage collection will occur; the
+ * pointer must later be freed with free().  This is for memory
+ * allocations of types (b) and (c).
 /* register @ptr in @gc for free on exit from outermost libxl callframe. */
-_hidden void libxl__ptr_add(libxl__gc *gc, void *ptr);
+_hidden void libxl__ptr_add(libxl__gc *gc_opt, void *ptr);
 /* if this is the outermost libxl callframe then free all pointers in @gc */
 _hidden void libxl__free_all(libxl__gc *gc);
 /* allocate and zero @bytes. (similar to a gc'd malloc(3)+memzero()) */
-_hidden void *libxl__zalloc(libxl__gc *gc, int bytes);
+_hidden void *libxl__zalloc(libxl__gc *gc_opt, int bytes);
 /* allocate and zero memory for an array of @nmemb members of @size each.
  * (similar to a gc'd calloc(3)). */
-_hidden void *libxl__calloc(libxl__gc *gc, size_t nmemb, size_t size);
+_hidden void *libxl__calloc(libxl__gc *gc_opt, size_t nmemb, size_t size);
 /* change the size of the memory block pointed to by @ptr to @new_size bytes.
  * unlike other allocation functions here any additional space between the
  * oldsize and @new_size is not initialised (similar to a gc'd realloc(3)). */
-_hidden void *libxl__realloc(libxl__gc *gc, void *ptr, size_t new_size);
+_hidden void *libxl__realloc(libxl__gc *gc_opt, void *ptr, size_t new_size);
 /* print @fmt into an allocated string large enoughto contain the result.
  * (similar to gc'd asprintf(3)). */
-_hidden char *libxl__sprintf(libxl__gc *gc, const char *fmt, ...) 
+_hidden char *libxl__sprintf(libxl__gc *gc_opt, const char *fmt, ...) 
 /* duplicate the string @c (similar to a gc'd strdup(3)). */
-_hidden char *libxl__strdup(libxl__gc *gc, const char *c);
+_hidden char *libxl__strdup(libxl__gc *gc_opt, const char *c);
 /* duplicate at most @n bytes of string @c (similar to a gc'd strndup(3)). */
-_hidden char *libxl__strndup(libxl__gc *gc, const char *c, size_t n);
+_hidden char *libxl__strndup(libxl__gc *gc_opt, const char *c, size_t n);
 /* strip the last path component from @s and return as a newly allocated
  * string. (similar to a gc'd dirname(3)). */
-_hidden char *libxl__dirname(libxl__gc *gc, const char *s);
+_hidden char *libxl__dirname(libxl__gc *gc_opt, const char *s);
 _hidden char **libxl__xs_kvs_of_flexarray(libxl__gc *gc, flexarray_t *array, 
int length);

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