Hi,

I've been trying to run Postgis regress tests under Clang sanitizers and one of
the issues I'm facing is the constant stream of errors during the `configure`
step coming from calls to `pg_config`.

Example:
```
$ pg_config --cc
clang

=================================================================
==14521==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 368 byte(s) in 1 object(s) allocated from:
    #0 0x55de20d161d9 in malloc (/usr/bin/pg_config+0xf81d9)
[...]

SUMMARY: AddressSanitizer: 2610 byte(s) leaked in 47 allocation(s).
```

The leaked memory is part of the `configdata` array which isn't freed before
exiting. It doesn't have any long term impact but it's annoying.

A similar thing happens in the `pg_config` SQL function. Since the memory
will be released at the end of the transaction, releasing it is optional but
I've done it anyway.

I'm attaching a the patch with the changes.

Greetings,

Greetings,

-- 
Raúl Marín Rodríguez
carto.com
From 0d35d7a21b87554df7ef27b70dcf7e4ea512699f Mon Sep 17 00:00:00 2001
From: Raul Marin <git@rmr.ninja>
Date: Wed, 14 Nov 2018 09:08:50 +0100
Subject: [PATCH] pg_config: Avoid leaking configdata

---
 src/backend/utils/misc/pg_config.c |  1 +
 src/bin/pg_config/pg_config.c      |  4 ++++
 src/common/config_info.c           | 15 ++++++++++++++-
 src/include/common/config_info.h   |  2 ++
 4 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/backend/utils/misc/pg_config.c b/src/backend/utils/misc/pg_config.c
index aa434bc3ab..62d1aea287 100644
--- a/src/backend/utils/misc/pg_config.c
+++ b/src/backend/utils/misc/pg_config.c
@@ -78,6 +78,7 @@ pg_config(PG_FUNCTION_ARGS)
 		tuple = BuildTupleFromCStrings(attinmeta, values);
 		tuplestore_puttuple(tupstore, tuple);
 	}
+	free_configdata(configdata, configdata_len);
 
 	/*
 	 * no longer need the tuple descriptor reference created by
diff --git a/src/bin/pg_config/pg_config.c b/src/bin/pg_config/pg_config.c
index a341b756de..c53a802422 100644
--- a/src/bin/pg_config/pg_config.c
+++ b/src/bin/pg_config/pg_config.c
@@ -160,6 +160,7 @@ main(int argc, char **argv)
 	{
 		for (i = 0; i < configdata_len; i++)
 			printf("%s = %s\n", configdata[i].name, configdata[i].setting);
+		free_configdata(configdata, configdata_len);
 		exit(0);
 	}
 
@@ -180,9 +181,12 @@ main(int argc, char **argv)
 			fprintf(stderr, _("%s: invalid argument: %s\n"),
 					progname, argv[i]);
 			advice();
+			free_configdata(configdata, configdata_len);
 			exit(1);
 		}
 	}
 
+	free_configdata(configdata, configdata_len);
+
 	return 0;
 }
diff --git a/src/common/config_info.c b/src/common/config_info.c
index 55e688e656..f8da71c598 100644
--- a/src/common/config_info.c
+++ b/src/common/config_info.c
@@ -27,7 +27,7 @@
  * get_configdata(const char *my_exec_path, size_t *configdata_len)
  *
  * Get configure-time constants. The caller is responsible
- * for pfreeing the result.
+ * for pfreeing the result [free_configdata]
  */
 ConfigData *
 get_configdata(const char *my_exec_path, size_t *configdata_len)
@@ -203,3 +203,16 @@ get_configdata(const char *my_exec_path, size_t *configdata_len)
 
 	return configdata;
 }
+
+
+void
+free_configdata(ConfigData *configdata, size_t configdata_len)
+{
+	int i;
+	for (i = 0; i < configdata_len; i++)
+	{
+		pfree(configdata[i].name);
+		pfree(configdata[i].setting);
+	}
+	pfree(configdata);
+}
diff --git a/src/include/common/config_info.h b/src/include/common/config_info.h
index 72014a915a..26f85e86a9 100644
--- a/src/include/common/config_info.h
+++ b/src/include/common/config_info.h
@@ -18,4 +18,6 @@ typedef struct ConfigData
 extern ConfigData *get_configdata(const char *my_exec_path,
 			   size_t *configdata_len);
 
+extern void free_configdata(ConfigData *configdata, size_t configdata_len);
+
 #endif							/* COMMON_CONFIG_INFO_H */
-- 
2.19.1

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