7 files changed, 22 insertions, 20 deletions

diff --git a/compiler.c b/compiler.c
index 07271c3..b880cf8 100644
--- a/compiler.c
+++ b/compiler.c
@@ -351,7 +351,7 @@ vm_op_t *bp_simplepattern(file_t *f, const char *str)
         // Parentheses
         case '(': case '{': {
             char closing = c == '(' ? ')' : '}';
-            free(op);
+            xfree(&op);
             op = bp_simplepattern(f, str);
             if (!op)
                 file_err(f, str, str, "There should be a valid pattern after this parenthesis.");
@@ -428,8 +428,8 @@ vm_op_t *bp_simplepattern(file_t *f, const char *str)
                 op->args.s = strndup(&c, 1);
             }
             if (matchchar(&str, ':')) { // Don't match definitions
-                free((char*)op->args.s);
-                free(op);
+                xfree(&op->args.s);
+                xfree(&op);
                 return NULL;
             }
             op->op = VM_REF;
@@ -442,14 +442,14 @@ vm_op_t *bp_simplepattern(file_t *f, const char *str)
                 const char *refname = str;
                 str = after_name(str);
                 if (matchchar(&str, ':')) { // Don't match definitions
-                    free(op);
+                    xfree(&op);
                     return NULL;
                 }
                 op->op = VM_REF;
                 op->args.s = strndup(refname, (size_t)(str - refname));
                 break;
             } else {
-                free(op);
+                xfree(&op);
                 return NULL;
             }
         }
@@ -535,8 +535,7 @@ vm_op_t *bp_stringpattern(file_t *f, const char *str)
         strop->end = str;
 
         if (strop->len == 0) {
-            free(strop);
-            strop = NULL;
+            xfree(&strop);
         } else {
             ret = chain_together(ret, strop);
         }
diff --git a/file_loader.c b/file_loader.c
index 1f61953..c5dc222 100644
--- a/file_loader.c
+++ b/file_loader.c
@@ -103,30 +103,29 @@ void intern_file(file_t *f)
     f->contents = buf;
     f->end = buf + size;
     f->mmapped = 0;
-    free(f->lines);
+    xfree(&f->lines);
     populate_lines(f);
 }
 
 void destroy_file(file_t **f)
 {
     if ((*f)->filename) {
-        free((char*)(*f)->filename);
+        xfree(&((*f)->filename));
         (*f)->filename = NULL;
     }
     if ((*f)->lines) {
-        free((*f)->lines);
+        xfree(&((*f)->lines));
         (*f)->lines = NULL;
     }
     if ((*f)->contents) {
         if ((*f)->mmapped) {
             munmap((*f)->contents, (size_t)((*f)->end - (*f)->contents));
         } else {
-            free((*f)->contents);
+            xfree(&((*f)->contents));
         }
         (*f)->contents = NULL;
     }
-    free(*f);
-    *f = NULL;
+    xfree(f);
 }
 
 size_t get_line_number(file_t *f, const char *p)
diff --git a/grammar.c b/grammar.c
index f287f46..b980196 100644
--- a/grammar.c
+++ b/grammar.c
@@ -119,8 +119,8 @@ void pop_backrefs(grammar_t *g, size_t count)
         backref_t *b = g->firstbackref;
         g->firstbackref = b->next;
         check(b, "Attempt to pop %ld more backrefs than there are", count);
-        xfree((void**)&b->op);
-        xfree((void**)&b);
+        xfree(&b->op);
+        xfree(&b);
     }
 }
 
diff --git a/printing.c b/printing.c
index 68faf22..e8cd178 100644
--- a/printing.c
+++ b/printing.c
@@ -132,7 +132,7 @@ static void _visualize_matches(match_node_t *firstmatch, int depth, const char *
 
     for (match_node_t *c = children, *next = NULL; c; c = next) {
         next = c->next;
-        free(c);
+        xfree(&c);
     }
 }
 
diff --git a/utils.c b/utils.c
index c18ef9e..f13db19 100644
--- a/utils.c
+++ b/utils.c
@@ -214,9 +214,13 @@ int memicmp(const void *v1, const void *v2, size_t n)
 /*
  * Free memory, but also set the pointer to NULL for safety
  */
-void xfree(void **p)
+void xfree(void *p)
 {
-    free(*p);
+    if (*(void**)p == NULL) {
+        fprintf(stderr, "Attempt to free(NULL)\n");
+        _exit(1);
+    }
+    free(*(void**)p);
     p = NULL;
 }
 
diff --git a/utils.h b/utils.h
index 7fde16f..8fcb345 100644
--- a/utils.h
+++ b/utils.h
@@ -34,7 +34,7 @@ void *memcheck(void *p);
 __attribute__((nonnull))
 int memicmp(const void *s1, const void *s2, size_t n);
 __attribute__((nonnull))
-void xfree(void **p);
+void xfree(void *p);
 
 #endif
 // vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1
diff --git a/vm.c b/vm.c
index 55c25fb..78eade4 100644
--- a/vm.c
+++ b/vm.c
@@ -538,7 +538,7 @@ match_t *get_capture(match_t *m, const char **r)
         if (end == *r) return NULL;
         char *name = strndup(*r, (size_t)(end-*r));
         match_t *cap = get_capture_by_name(m, name);
-        free(name);
+        xfree(&name);
         *r = end;
         if (**r == ';') ++(*r);
         return cap;