Demacro modernization of NewSList to plug a memory leak during error handling

atobm.c:248:6: warning: Potential leak of memory pointed to by 'slist'
            NewSList ();
            ^~~~~~~~~~~
atobm.c:209:3: note: expanded from macro 'NewSList'
                fprintf (stderr, "%s:  unable to allocate char array\n", \
                ^~~~~~~
atobm.c:259:6: warning: Potential leak of memory pointed to by 'old'
            NewSList ();
            ^~~~~~~~~~~
atobm.c:209:3: note: expanded from macro 'NewSList'
                fprintf (stderr, "%s:  unable to allocate char array\n", \
                ^~~~~~~
atobm.c:259:6: warning: Potential leak of memory pointed to by 'slist'
            NewSList ();
            ^~~~~~~~~~~
atobm.c:209:3: note: expanded from macro 'NewSList'
                fprintf (stderr, "%s:  unable to allocate char array\n", \
                ^~~~~~~
3 warnings generated.

Signed-off-by: Jeremy Huddleston Sequoia <jeremyhu@apple.com>

1 files changed, 39 insertions, 28 deletions

diff --git a/atobm.c b/atobm.c
index ef6da7e..44fdcda 100644
--- a/atobm.c
+++ b/atobm.c
@@ -167,6 +167,31 @@ main (int argc, char *argv[])
     exit (0);
 }
 
+struct _scan_list {
+    int allocated;
+    int used;
+    unsigned char *scanlines;
+    struct _scan_list *next;
+};
+
+#define NTOALLOC 16
+static inline struct _scan_list *
+_new_scan_list(int bytes_per_scanline) {
+    struct _scan_list *slist = (struct _scan_list *) calloc (1, sizeof(*slist));
+    if (!slist) {
+	return NULL;
+    }
+    slist->allocated = NTOALLOC * bytes_per_scanline;
+    slist->scanlines = (unsigned char *) calloc(slist->allocated, 1);
+    if (!slist->scanlines) {
+        free(slist);
+        return NULL;
+    }
+    slist->used = 0;
+    slist->next = NULL;
+
+    return slist;
+}
 
 static void
 doit (FILE *fp,
@@ -185,34 +210,11 @@ doit (FILE *fp,
 			(isascii(chars[1]) && isspace(chars[1]))) ? 0 : 1);
     int lineno = 0;
     int bytes_per_scanline = 0;
-    struct _scan_list {
-	int allocated;
-	int used;
-	unsigned char *scanlines;
-	struct _scan_list *next;
-    } *head = NULL, *slist = NULL;
+    struct _scan_list *head = NULL, *slist = NULL;
     static unsigned char masktable[] = {
 	0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80 };
     int padded = 0;
 
-#define NTOALLOC 16
-#define NewSList() \
-	    slist = (struct _scan_list *) calloc (1, sizeof *slist); \
-	    if (!slist) { \
-		fprintf (stderr, "%s:  unable to allocate scan list\n", \
-			 ProgramName); \
-		return; \
-	    } \
-	    slist->allocated = NTOALLOC * bytes_per_scanline; \
-	    slist->scanlines = (unsigned char *) calloc(slist->allocated, 1); \
-	    if (!slist->scanlines) { \
-		fprintf (stderr, "%s:  unable to allocate char array\n", \
-			 ProgramName); \
-		return; \
-	    } \
-	    slist->used = 0; \
-	    slist->next = NULL;
-
     while (1) {
 	buf[0] = '\0';
 	lineno++;
@@ -245,8 +247,12 @@ doit (FILE *fp,
 	    width = len;
 	    padded = ((width & 7) != 0);
 	    bytes_per_scanline = (len + 7) / 8;
-	    NewSList ();
-	    head = slist;
+	    head = slist = _new_scan_list(bytes_per_scanline);
+
+            if (!slist) {
+                fprintf (stderr, "%s:  unable to allocate scan list\n", ProgramName);
+                return;
+            }
 	} else if (width != len) {
 	    fprintf (stderr,
 		     "%s:  line %d is %d characters wide instead of %d\n",
@@ -256,8 +262,13 @@ doit (FILE *fp,
 
 	if (slist->used + 1 >= slist->allocated) {
 	    struct _scan_list *old = slist;
-	    NewSList ();
-	    old->next = slist;
+	    old->next = slist = _new_scan_list(bytes_per_scanline);
+
+	    if (!slist) {
+	        fprintf (stderr, "%s:  unable to allocate scan list\n", ProgramName);
+		free(old);
+	        return;
+	    }
 	}
 
 	/* okay, parse the line and stick values into the scanline array */