X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/3d88e64dfcf5dc0fd361ce0c504c67a9196ce44c..a607fe54c9f20934b57e29e9040b9dd0a4decf3a:/puttymem.h

diff --git a/puttymem.h b/puttymem.h
index 9fe272fd..941aded3 100644
--- a/puttymem.h
+++ b/puttymem.h
@@ -11,18 +11,22 @@
 
 /* #define MALLOC_LOG  do this if you suspect putty of leaking memory */
 #ifdef MALLOC_LOG
-#define smalloc(z) (mlog(__FILE__,__LINE__), safemalloc(z))
-#define srealloc(y,z) (mlog(__FILE__,__LINE__), saferealloc(y,z))
+#define smalloc(z) (mlog(__FILE__,__LINE__), safemalloc(z,1))
+#define snmalloc(z,s) (mlog(__FILE__,__LINE__), safemalloc(z,s))
+#define srealloc(y,z) (mlog(__FILE__,__LINE__), saferealloc(y,z,1))
+#define snrealloc(y,z,s) (mlog(__FILE__,__LINE__), saferealloc(y,z,s))
 #define sfree(z) (mlog(__FILE__,__LINE__), safefree(z))
 void mlog(char *, int);
 #else
-#define smalloc safemalloc
-#define srealloc saferealloc
+#define smalloc(z) safemalloc(z,1)
+#define snmalloc safemalloc
+#define srealloc(y,z) saferealloc(y,z,1)
+#define snrealloc saferealloc
 #define sfree safefree
 #endif
 
-void *safemalloc(size_t);
-void *saferealloc(void *, size_t);
+void *safemalloc(size_t, size_t);
+void *saferealloc(void *, size_t, size_t);
 void safefree(void *);
 
 /*
@@ -30,9 +34,19 @@ void safefree(void *);
  * possible, in favour of these type-casting macros which ensure
  * you don't mistakenly allocate enough space for one sort of
  * structure and assign it to a different sort of pointer.
+ *
+ * The nasty trick in sresize with sizeof arranges for the compiler,
+ * in passing, to type-check the expression ((type *)0 == (ptr)), i.e.
+ * to type-check that the input pointer is a pointer to the correct
+ * type. The construction sizeof(stuff) ? (b) : (b) looks like a
+ * violation of the first principle of safe macros, but in fact it's
+ * OK - although it _expands_ the macro parameter more than once, it
+ * only _evaluates_ it once, so it's still side-effect safe.
  */
-#define snew(type) ((type *)smalloc(sizeof(type)))
-#define snewn(n, type) ((type *)smalloc((n)*sizeof(type)))
-#define sresize(ptr, n, type) ((type *)srealloc(ptr, (n)*sizeof(type)))
+#define snew(type) ((type *)snmalloc(1, sizeof(type)))
+#define snewn(n, type) ((type *)snmalloc((n), sizeof(type)))
+#define sresize(ptr, n, type)                                           \
+    ((type *)snrealloc(sizeof((type *)0 == (ptr)) ? (ptr) : (ptr),      \
+                       (n), sizeof(type)))
 
 #endif