[avr-libc-commit] [2400] GCC 4.5+ implies malloc() and free() have no side-effects to global

[Joerg Wunsch]

Revision: 2400
          http://svn.sv.gnu.org/viewvc/?view=rev&root=avr-libc&revision=2400
Author:   joerg_wunsch
Date:     2013-05-13 15:21:58 +0000 (Mon, 13 May 2013)
Log Message:
-----------
GCC 4.5+ implies malloc() and free() have no side-effects to global
variables.  Place a memory barrier before any evaluations of __flp or
__brkval to ensure the compiler actually reads them from the
respective memory locations.

Replace private library definitions by "stdlib_private.h".

Modified Paths:
--------------
    trunk/avr-libc/ChangeLog
    trunk/avr-libc/tests/simulate/stdlib/malloc-7.c
    trunk/avr-libc/tests/simulate/stdlib/realloc-2.c

Modified: trunk/avr-libc/ChangeLog
===================================================================
--- trunk/avr-libc/ChangeLog    2013-05-13 15:12:10 UTC (rev 2399)
+++ trunk/avr-libc/ChangeLog    2013-05-13 15:21:58 UTC (rev 2400)
@@ -5,6 +5,9 @@
        memory barrier before any evaluations of __flp or __brkval to
        ensure the compiler actually reads them from the respective memory
        locations.
+       * tests/simulate/stdlib/malloc-7.c: (Dito.)  Also replace private
+       library definitions by "stdlib_private.h"
+       * tests/simulate/stdlib/realloc-2.c: (Dito.)
 
 2013-05-08  Joerg Wunsch <address@hidden>
 

Modified: trunk/avr-libc/tests/simulate/stdlib/malloc-7.c
===================================================================
--- trunk/avr-libc/tests/simulate/stdlib/malloc-7.c     2013-05-13 15:12:10 UTC 
(rev 2399)
+++ trunk/avr-libc/tests/simulate/stdlib/malloc-7.c     2013-05-13 15:21:58 UTC 
(rev 2400)
@@ -43,17 +43,10 @@
 
 #include <stdint.h>
 #include <stdlib.h>
+#include <avr/cpufunc.h>
 
-struct __freelist {
-        size_t sz;
-        struct __freelist *nx;
-};
+#include "../../libc/stdlib/stdlib_private.h"
 
-extern char *__brkval;          /* first location not yet allocated */
-extern struct __freelist *__flp; /* freelist pointer (head of freelist) */
-extern char *__malloc_heap_start;
-extern char *__malloc_heap_end;
-
 int main(void)
 {
     void *ptrs[6];
@@ -67,11 +60,13 @@
     }
 
     free(ptrs[5]);
+    _MemoryBarrier();
     /* Freelist must be still empty, and __brkval reduced. */
     if (__flp != NULL) return __LINE__;
     if ((char *)(ptrs[5]) - 2 != __brkval) return __LINE__;
 
     free(ptrs[4]);
+    _MemoryBarrier();
     /* Still no entry, and __brkval further down. */
     if (__flp != NULL) return __LINE__;
     if ((char *)(ptrs[4]) - 2 != __brkval) return __LINE__;
@@ -79,17 +74,20 @@
     struct __freelist *ofp = __flp;
 
     free(ptrs[1]);
+    _MemoryBarrier();
     /* One entry added. */
     if ((char *)(ptrs[1]) - 2 != (void *)__flp) return __LINE__;
     if (__flp->sz != 10) return __LINE__;
     if (__flp->nx != (void *)ofp) return __LINE__;
 
     free(ptrs[3]);
+    _MemoryBarrier();
     /* __brkval lowered again. */
     if (__flp->nx != NULL) return __LINE__;
     if ((char *)(ptrs[3]) - 2 != __brkval) return __LINE__;
 
     free(ptrs[2]);
+    _MemoryBarrier();
     /* ...and again. */
     if (__flp->nx != NULL) return __LINE__;
     if ((char *)(ptrs[1]) - 2 != __brkval) return __LINE__;

Modified: trunk/avr-libc/tests/simulate/stdlib/realloc-2.c
===================================================================
--- trunk/avr-libc/tests/simulate/stdlib/realloc-2.c    2013-05-13 15:12:10 UTC 
(rev 2399)
+++ trunk/avr-libc/tests/simulate/stdlib/realloc-2.c    2013-05-13 15:21:58 UTC 
(rev 2400)
@@ -44,17 +44,10 @@
 
 #include <stdint.h>
 #include <stdlib.h>
+#include <avr/cpufunc.h>
 
-struct __freelist {
-        size_t sz;
-        struct __freelist *nx;
-};
+#include "../../libc/stdlib/stdlib_private.h"
 
-extern char *__brkval;          /* first location not yet allocated */
-extern struct __freelist *__flp; /* freelist pointer (head of freelist) */
-extern char *__malloc_heap_start;
-extern char *__malloc_heap_end;
-
 #if defined(__AVR_ATmega128__)
 static const int sizes[8] =
 {
@@ -84,6 +77,7 @@
         if (p == NULL) return __LINE__;
         ptrs[i] = p;
     }
+    _MemoryBarrier();
     /* second test: the amount of memory allocated to the heap must
        match the expected TARGETVAL */
     if (__brkval - __malloc_heap_start != TARGETVAL) return __LINE__;
@@ -95,6 +89,7 @@
         free(ptrs[i]);
     }
 
+    _MemoryBarrier();
     /* after freeing everything, the freelist must be empty */
     if (__flp != NULL) return __LINE__;
     if (__brkval != __malloc_heap_start) return __LINE__;
@@ -110,6 +105,7 @@
         if (q != p) return __LINE__;
     }
 
+    _MemoryBarrier();
     /* Verify the allocation length did not increase. */
     if (__brkval > obrk) return __LINE__;