OS-4498 custr_cstr() should never return NULL

Reviewed by: Patrick Mooney <patrick.mooney@joyent.com>
Reviewed by: Cody Mello <cody.mello@joyent.com>

3 files changed, 19 insertions, 18 deletions

diff --git a/usr/src/common/brand/lx/tools/gen_errno.c b/usr/src/common/brand/lx/tools/gen_errno.c
index 1edd924edf..52b2d76d24 100644
--- a/usr/src/common/brand/lx/tools/gen_errno.c
+++ b/usr/src/common/brand/lx/tools/gen_errno.c
@@ -185,12 +185,8 @@ process_line(const char *line, nvlist_t *nvl)
 	if (custr_alloc(&nam) != 0 || custr_alloc(&num) != 0) {
 		int en = errno;
 
-		if (nam != NULL) {
-			custr_free(nam);
-		}
-		if (num != NULL) {
-			custr_free(num);
-		}
+		custr_free(nam);
+		custr_free(num);
 
 		errno = en;
 		return (-1);
@@ -282,14 +278,12 @@ read_file_into_list(const char *path, nvlist_t *nvl)
 	FILE *f;
 	custr_t *cu = NULL;
 
-	if (custr_alloc(&cu) != 0 || custr_append(cu, "") != 0) {
-		if (cu != NULL) {
-			custr_free(cu);
-		}
+	if (custr_alloc(&cu) != 0) {
 		return (-1);
 	}
 
 	if ((f = fopen(path, "r")) == NULL) {
+		custr_free(cu);
 		return (-1);
 	}
 
diff --git a/usr/src/lib/libcmdutils/common/custr.c b/usr/src/lib/libcmdutils/common/custr.c
index 03a9561934..8da7b98ac2 100644
--- a/usr/src/lib/libcmdutils/common/custr.c
+++ b/usr/src/lib/libcmdutils/common/custr.c
@@ -14,7 +14,7 @@
  */
 
 /*
- * Copyright 2014, Joyent, Inc.
+ * Copyright 2015 Joyent, Inc.
  */
 
 #include <stdlib.h>
@@ -22,6 +22,7 @@
 #include <string.h>
 #include <stdio.h>
 #include <stdarg.h>
+#include <sys/debug.h>
 
 #include "libcmdutils.h"
 
@@ -57,6 +58,16 @@ custr_len(custr_t *cus)
 const char *
 custr_cstr(custr_t *cus)
 {
+	if (cus->cus_data == NULL) {
+		VERIFY(cus->cus_strlen == 0);
+		VERIFY(cus->cus_datalen == 0);
+
+		/*
+		 * This function should never return NULL.  If no buffer has
+		 * been allocated, return a pointer to a zero-length string.
+		 */
+		return ("");
+	}
 	return (cus->cus_data);
 }
 
diff --git a/usr/src/lib/varpd/files/common/libvarpd_files_json.c b/usr/src/lib/varpd/files/common/libvarpd_files_json.c
index 66aaefb29b..240c84bd77 100644
--- a/usr/src/lib/varpd/files/common/libvarpd_files_json.c
+++ b/usr/src/lib/varpd/files/common/libvarpd_files_json.c
@@ -311,9 +311,7 @@ hdlr_bareword(state_t *s)
 		return;
 	}
 
-	if ((str = custr_cstr(s->s_collect)) != NULL) {
-		abort();
-	}
+	str = custr_cstr(s->s_collect);
 	if (strcmp(str, "true") == 0) {
 		s->s_top->pf_value_type = JSON_TYPE_BOOLEAN;
 		s->s_top->pf_value = (void *)B_TRUE;
@@ -828,11 +826,9 @@ nvlist_parse_json(const char *buf, size_t buflen, nvlist_t **nvlp,
 	s.s_flags = flag;
 
 	/*
-	 * Allocate the collect buffer string and ensure it is backed by at
-	 * least some string memory.
+	 * Allocate the collect buffer string.
 	 */
-	if (custr_alloc(&s.s_collect) != 0 ||
-	    custr_append(s.s_collect, "") != 0) {
+	if (custr_alloc(&s.s_collect) != 0) {
 		s.s_errno = errno;
 		if (errout != NULL) {
 			(void) snprintf(errout->nje_message,