Changed the behaviour of realloc() in Memcheck, Addrcheck and Helgrind.

Previously, when realloc() was asked to make a block bigger, the ExeContext
describing where that block was allocated was increased;  however, if the block
became smaller or stayed the same size, the original ExeContext remained.  This
is correct in one way (that's where the memory manager actually parcelled out
the block) but it's not very intuitive.  This commit changes things so the
ExeContext of a block is always changed upon realloc().  I added a regression
test for it too.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@1783

helgrind/hg_main.c

@@ -1965,11 +1965,13 @@ void* SK_(realloc) ( void* p, Int new_size )
   
    if (hc->size == new_size) {
       /* size unchanged */
+      hc->where = VG_(get_ExeContext)(tid);
       return p;
       
    } else if (hc->size > new_size) {
       /* new size is smaller */
       hc->size = new_size;
+      hc->where = VG_(get_ExeContext)(tid);
       return p;
 
    } else {

memcheck/mac_malloc_wrappers.c

@@ -354,6 +354,7 @@ void* SK_(realloc) ( void* p, Int new_size )
 
    if (mc->size == new_size) {
       /* size unchanged */
+      mc->where = VG_(get_ExeContext)(tid);
       VGP_POPCC(VgpCliMalloc);
       return p;
       
@@ -361,6 +362,7 @@ void* SK_(realloc) ( void* p, Int new_size )
       /* new size is smaller */
       MAC_(die_mem_heap)( mc->data+new_size, mc->size-new_size );
       mc->size = new_size;
+      mc->where = VG_(get_ExeContext)(tid);
       VGP_POPCC(VgpCliMalloc);
       return p;
 

memcheck/tests/Makefile.am

@@ -44,6 +44,7 @@ EXTRA_DIST = $(noinst_SCRIPTS) \
 	pushfpopf.stderr.exp pushfpopf.stdout.exp pushfpopf.vgtest \
 	realloc1.stderr.exp realloc1.vgtest \
 	realloc2.stderr.exp realloc2.vgtest \
+	realloc3.stderr.exp realloc3.vgtest \
 	sigaltstack.stderr.exp sigaltstack.vgtest \
 	signal2.stderr.exp \
 	signal2.stdout.exp signal2.vgtest \
@@ -64,7 +65,7 @@ check_PROGRAMS = \
 	malloc1 malloc2 malloc3 manuel1 manuel2 manuel3 \
 	memalign_test memcmptest mmaptest nanoleak null_socket \
 	overlap pushfpopf \
-	realloc1 realloc2 sigaltstack signal2 supp1 supp2 suppfree \
+	realloc1 realloc2 realloc3 sigaltstack signal2 supp1 supp2 suppfree \
 	trivialleak tronical weirdioctl	\
 	mismatches new_override metadata threadederrno
 
@@ -103,6 +104,7 @@ overlap_SOURCES 	= overlap.c
 pushfpopf_SOURCES 	= pushfpopf_c.c pushfpopf_s.s
 realloc1_SOURCES 	= realloc1.c
 realloc2_SOURCES 	= realloc2.c
+realloc3_SOURCES 	= realloc3.c
 signal2_SOURCES 	= signal2.c
 supp1_SOURCES 		= supp.c
 supp2_SOURCES 		= supp.c

memcheck/tests/realloc3.c

@@ -0,0 +1,28 @@
+/* For a long time (from Valgrind 1.0 to 1.9.6, AFAICT) when realloc() was
+   called and made a block smaller, or didn't change its size, the
+   ExeContext of the block was not updated;  therefore any errors that
+   referred to it would state that it was allocated not by the realloc(),
+   but by the previous malloc() or whatever.  While this is true in one
+   sense, it is misleading and not what you'd expect.  This test
+   demonstrates this -- 'x' and 'y' are unchanged and shrunk, and their
+   ExeContexts should be updated upon their realloc().  I hope that's clear.
+*/
+#include <stdlib.h>
+
+int main(void)
+{
+   int* x = malloc(5);
+   int* y = malloc(10);
+   int* z = malloc(2);
+   int a, b, c;
+
+   x = realloc(x, 5);   // same size
+   y = realloc(y, 5);   // make smaller
+   z = realloc(z, 5);   // make bigger
+
+   a = (x[5] == 0xdeadbeef ? 1 : 0);
+   b = (y[5] == 0xdeadbeef ? 1 : 0);
+   c = (z[5] == 0xdeadbeef ? 1 : 0);
+
+   return a + b + c;
+}

memcheck/tests/realloc3.stderr.exp

@@ -0,0 +1,29 @@
+Invalid read of size 4
+   at 0x........: main (realloc3.c:23)
+   by 0x........: __libc_start_main (...libc...)
+   by 0x........: ...
+   Address 0x........ is 15 bytes after a block of size 5 alloc'd
+   at 0x........: realloc (vg_replace_malloc.c:...)
+   by 0x........: main (realloc3.c:19)
+   by 0x........: __libc_start_main (...libc...)
+   by 0x........: ...
+
+Invalid read of size 4
+   at 0x........: main (realloc3.c:24)
+   by 0x........: __libc_start_main (...libc...)
+   by 0x........: ...
+   Address 0x........ is 15 bytes after a block of size 5 alloc'd
+   at 0x........: realloc (vg_replace_malloc.c:...)
+   by 0x........: main (realloc3.c:20)
+   by 0x........: __libc_start_main (...libc...)
+   by 0x........: ...
+
+Invalid read of size 4
+   at 0x........: main (realloc3.c:25)
+   by 0x........: __libc_start_main (...libc...)
+   by 0x........: ...
+   Address 0x........ is 15 bytes after a block of size 5 alloc'd
+   at 0x........: realloc (vg_replace_malloc.c:...)
+   by 0x........: main (realloc3.c:21)
+   by 0x........: __libc_start_main (...libc...)
+   by 0x........: ...

memcheck/tests/realloc3.vgtest

@@ -0,0 +1,2 @@
+prog: realloc3
+vgopts: -q