Work around unportable behavior of malloc(0) and realloc(NULL, 0).

On some platforms these functions return NULL, rather than the more common
practice of returning a pointer to a zero-sized block of memory.  Hack our
various wrapper functions to hide the difference by substituting a size
request of 1.  This is probably not so important for the callers, who
should never touch the block anyway if they asked for size 0 --- but it's
important for the wrapper functions themselves, which mistakenly treated
the NULL result as an out-of-memory failure.  This broke at least pg_dump
for the case of no user-defined aggregates, as per report from
Matthew Carrington.

Back-patch to 9.2 to fix the pg_dump issue.  Given the lack of previous
complaints, it seems likely that there is no live bug in previous releases,
even though some of these functions were in place before that.

8 files changed, 37 insertions, 2 deletions

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 7f54d452eae..9ab13475575 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -3352,6 +3352,9 @@ guc_malloc(int elevel, size_t size)
 {
 	void	   *data;
 
+	/* Avoid unportable behavior of malloc(0) */
+	if (size == 0)
+		size = 1;
 	data = malloc(size);
 	if (data == NULL)
 		ereport(elevel,
@@ -3365,6 +3368,9 @@ guc_realloc(int elevel, void *old, size_t size)
 {
 	void	   *data;
 
+	/* Avoid unportable behavior of realloc(NULL, 0) */
+	if (old == NULL && size == 0)
+		size = 1;
 	data = realloc(old, size);
 	if (data == NULL)
 		ereport(elevel,
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 74046b5dfea..a2f16a01c3c 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -285,6 +285,9 @@ pg_malloc(size_t size)
 {
 	void	   *result;
 
+	/* Avoid unportable behavior of malloc(0) */
+	if (size == 0)
+		size = 1;
 	result = malloc(size);
 	if (!result)
 	{
diff --git a/src/bin/pg_basebackup/streamutil.c b/src/bin/pg_basebackup/streamutil.c
index c32c5acb2b9..e5fd6fd7655 100644
--- a/src/bin/pg_basebackup/streamutil.c
+++ b/src/bin/pg_basebackup/streamutil.c
@@ -54,6 +54,9 @@ xmalloc0(int size)
 {
 	void	   *result;
 
+	/* Avoid unportable behavior of malloc(0) */
+	if (size == 0)
+		size = 1;
 	result = malloc(size);
 	if (!result)
 	{
diff --git a/src/bin/pg_ctl/pg_ctl.c b/src/bin/pg_ctl/pg_ctl.c
index 72fc4c1abf6..b288e9a8a63 100644
--- a/src/bin/pg_ctl/pg_ctl.c
+++ b/src/bin/pg_ctl/pg_ctl.c
@@ -233,6 +233,9 @@ pg_malloc(size_t size)
 {
 	void	   *result;
 
+	/* Avoid unportable behavior of malloc(0) */
+	if (size == 0)
+		size = 1;
 	result = malloc(size);
 	if (!result)
 	{
diff --git a/src/bin/pg_dump/dumpmem.c b/src/bin/pg_dump/dumpmem.c
index 3ef10307bc5..cadc89d4447 100644
--- a/src/bin/pg_dump/dumpmem.c
+++ b/src/bin/pg_dump/dumpmem.c
@@ -42,6 +42,9 @@ pg_malloc(size_t size)
 {
 	void	   *tmp;
 
+	/* Avoid unportable behavior of malloc(0) */
+	if (size == 0)
+		size = 1;
 	tmp = malloc(size);
 	if (!tmp)
 		exit_horribly(NULL, "out of memory\n");
@@ -64,6 +67,9 @@ pg_realloc(void *ptr, size_t size)
 {
 	void	   *tmp;
 
+	/* Avoid unportable behavior of realloc(NULL, 0) */
+	if (ptr == NULL && size == 0)
+		size = 1;
 	tmp = realloc(ptr, size);
 	if (!tmp)
 		exit_horribly(NULL, "out of memory\n");
diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c
index 330d5ce12cf..c804148cd57 100644
--- a/src/bin/psql/common.c
+++ b/src/bin/psql/common.c
@@ -60,6 +60,9 @@ pg_malloc(size_t size)
 {
 	void	   *tmp;
 
+	/* Avoid unportable behavior of malloc(0) */
+	if (size == 0)
+		size = 1;
 	tmp = malloc(size);
 	if (!tmp)
 	{
diff --git a/src/bin/psql/print.c b/src/bin/psql/print.c
index 8fa5e371284..6da3ba053e0 100644
--- a/src/bin/psql/print.c
+++ b/src/bin/psql/print.c
@@ -136,6 +136,9 @@ pg_local_malloc(size_t size)
 {
 	void	   *tmp;
 
+	/* Avoid unportable behavior of malloc(0) */
+	if (size == 0)
+		size = 1;
 	tmp = malloc(size);
 	if (!tmp)
 	{
diff --git a/src/port/dirmod.c b/src/port/dirmod.c
index 22f5c591b07..514424f82e6 100644
--- a/src/port/dirmod.c
+++ b/src/port/dirmod.c
@@ -70,7 +70,11 @@ fe_palloc(Size size)
 {
 	void	   *res;
 
-	if ((res = malloc(size)) == NULL)
+	/* Avoid unportable behavior of malloc(0) */
+	if (size == 0)
+		size = 1;
+	res = malloc(size);
+	if (res == NULL)
 	{
 		fprintf(stderr, _("out of memory\n"));
 		exit(1);
@@ -96,7 +100,11 @@ fe_repalloc(void *pointer, Size size)
 {
 	void	   *res;
 
-	if ((res = realloc(pointer, size)) == NULL)
+	/* Avoid unportable behavior of realloc(NULL, 0) */
+	if (pointer == NULL && size == 0)
+		size = 1;
+	res = realloc(pointer, size);
+	if (res == NULL)
 	{
 		fprintf(stderr, _("out of memory\n"));
 		exit(1);