Allow size == 0 in isc_mem_{get,allocate,reallocate}

Calls to jemalloc extended API with size == 0 ends up in undefined
behaviour.  This commit makes the isc_mem_get() and friends calls
more POSIX aligned:

  If size is 0, either a null pointer or a unique pointer that can be
  successfully passed to free() shall be returned.

We picked the easier route (which have been already supported in the old
code) and return NULL on calls to the API where size == 0.

diff --git a/lib/isc/mem.c b/lib/isc/mem.c
index f023737098ee57182ba05fbce59d6c3e25ee0f8a..2b81d023856f357af9b50a819e9c7337291382ed 100644 (file)
--- a/lib/isc/mem.c
+++ b/lib/isc/mem.c
@@ -589,6 +589,7 @@ isc__mem_putanddetach(isc_mem_t **ctxp, void *ptr, size_t size FLARG) {
 
        REQUIRE(ctxp != NULL && VALID_CONTEXT(*ctxp));
        REQUIRE(ptr != NULL);
+       REQUIRE(size > 0);
 
        ctx = *ctxp;
        *ctxp = NULL;
@@ -713,9 +714,11 @@ isc__mem_get(isc_mem_t *ctx, size_t size FLARG) {
 
        REQUIRE(VALID_CONTEXT(ctx));
 
-       ptr = mem_get(ctx, size);
-       mem_getstats(ctx, size);
+       if (ISC_LIKELY(size != 0)) {
+               ptr = mem_get(ctx, size);
+       }
 
+       mem_getstats(ctx, size);
        ADD_TRACE(ctx, ptr, size, file, line);
 
        call_water = hi_water(ctx);
@@ -730,12 +733,15 @@ isc__mem_get(isc_mem_t *ctx, size_t size FLARG) {
 void
 isc__mem_put(isc_mem_t *ctx, void *ptr, size_t size FLARG) {
        REQUIRE(VALID_CONTEXT(ctx));
-       REQUIRE(ptr != NULL);
+       REQUIRE(ISC_LIKELY(ptr != NULL && size != 0) ||
+               ISC_UNLIKELY(ptr == NULL && size == 0));
 
        DELETE_TRACE(ctx, ptr, size, file, line);
 
        mem_putstats(ctx, ptr, size);
-       mem_put(ctx, ptr, size);
+       if (ISC_LIKELY(ptr != NULL)) {
+               mem_put(ctx, ptr, size);
+       }
 
        CALL_LO_WATER(ctx);
 }
@@ -856,10 +862,12 @@ isc__mem_allocate(isc_mem_t *ctx, size_t size FLARG) {
 
        REQUIRE(VALID_CONTEXT(ctx));
 
-       ptr = mem_get(ctx, size);
+       if (ISC_LIKELY(size != 0)) {
+               ptr = mem_get(ctx, size);
 
-       /* Recalculate the real allocated size */
-       size = sallocx(ptr, 0);
+               /* Recalculate the real allocated size */
+               size = sallocx(ptr, 0);
+       }
 
        mem_getstats(ctx, size);
        ADD_TRACE(ctx, ptr, size, file, line);
@@ -879,14 +887,9 @@ isc__mem_reallocate(isc_mem_t *ctx, void *old_ptr, size_t new_size FLARG) {
 
        REQUIRE(VALID_CONTEXT(ctx));
 
-       if (old_ptr == NULL) {
+       if (ISC_UNLIKELY(old_ptr == NULL)) {
                new_ptr = isc__mem_allocate(ctx, new_size FLARG_PASS);
-       } else if (new_size == 0) {
-               /*
-                * FIXME: We should not call isc__mem_reallocate with size == 0,
-                * this is undefined behaviour.  This code is kept only for
-                * backwards compatibility.
-                */
+       } else if (ISC_UNLIKELY(new_size == 0)) {
                isc__mem_free(ctx, old_ptr FLARG_PASS);
        } else {
                size_t old_size = sallocx(old_ptr, 0);
@@ -912,9 +915,9 @@ isc__mem_reallocate(isc_mem_t *ctx, void *old_ptr, size_t new_size FLARG) {
                ADD_TRACE(ctx, new_ptr, new_size, file, line);
 
                /*
-                * We want to postpone the call to water in edge case where the
-                * realloc will exactly hit on the boundary of the water and we
-                * would call water twice.
+                * We want to postpone the call to water in edge case
+                * where the realloc will exactly hit on the boundary of
+                * the water and we would call water twice.
                 */
                CALL_LO_WATER(ctx);
                CALL_HI_WATER(ctx);
@@ -925,17 +928,20 @@ isc__mem_reallocate(isc_mem_t *ctx, void *old_ptr, size_t new_size FLARG) {
 
 void
 isc__mem_free(isc_mem_t *ctx, void *ptr FLARG) {
-       size_t size;
+       size_t size = 0;
 
        REQUIRE(VALID_CONTEXT(ctx));
-       REQUIRE(ptr != NULL);
 
-       size = sallocx(ptr, 0);
+       if (ISC_LIKELY(ptr != NULL)) {
+               size = sallocx(ptr, 0);
+       }
 
        DELETE_TRACE(ctx, ptr, size, file, line);
 
        mem_putstats(ctx, ptr, size);
-       mem_put(ctx, ptr, size);
+       if (ISC_LIKELY(ptr != NULL)) {
+               mem_put(ctx, ptr, size);
+       }
 
        CALL_LO_WATER(ctx);
 }
@@ -956,9 +962,7 @@ isc__mem_strdup(isc_mem_t *mctx, const char *s FLARG) {
 
        ns = isc__mem_allocate(mctx, len FLARG_PASS);
 
-       if (ns != NULL) {
-               strlcpy(ns, s, len);
-       }
+       strlcpy(ns, s, len);
 
        return (ns);
 }
@@ -970,6 +974,7 @@ isc__mem_strndup(isc_mem_t *mctx, const char *s, size_t size FLARG) {
 
        REQUIRE(VALID_CONTEXT(mctx));
        REQUIRE(s != NULL);
+       REQUIRE(size != 0);
 
        len = strlen(s) + 1;
        if (len > size) {
@@ -978,9 +983,7 @@ isc__mem_strndup(isc_mem_t *mctx, const char *s, size_t size FLARG) {
 
        ns = isc__mem_allocate(mctx, len FLARG_PASS);
 
-       if (ns != NULL) {
-               strlcpy(ns, s, len);
-       }
+       strlcpy(ns, s, len);
 
        return (ns);
 }