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Bug 1410276 - Add a canary field to nsStringBuffer r=bz

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This version of the patch hopefully causes fewer performance regressions.
It might be good to apply this and catch some more assertions.
This commit is contained in:
Paul Bone
2017-11-09 15:17:35 +11:00
parent f6977620cf
commit e6f4fe0467
2 changed files with 66 additions and 1 deletions
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31
xpcom/string/nsSubstring.cpp
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@@ -20,6 +20,7 @@
#include "nsString.h"
#include "nsStringBuffer.h"
#include "nsDependentString.h"
#include "nsPrintfCString.h"
#include "nsMemory.h"
#include "prprf.h"
#include "nsStaticAtom.h"
@@ -36,6 +37,19 @@
#include <unistd.h>
#endif
#ifdef STRING_BUFFER_CANARY
#define CHECK_STRING_BUFFER_CANARY(c) \
do { \
if ((c) != CANARY_OK) { \
MOZ_CRASH_UNSAFE_PRINTF("Bad canary value %d", c); \
} \
} while(0)
#else
#define CHECK_STRING_BUFFER_CANARY(c) \
do { \
} while(0)
#endif
using mozilla::Atomic;
// ---------------------------------------------------------------------------
@@ -205,6 +219,8 @@ nsStringBuffer::AddRef()
void
nsStringBuffer::Release()
{
CHECK_STRING_BUFFER_CANARY(mCanary);
// Since this may be the last release on this thread, we need
// release semantics so that prior writes on this thread are visible
// to the thread that destroys the object when it reads mValue with
@@ -217,6 +233,9 @@ nsStringBuffer::Release()
// the last release on other threads, that is, to ensure that
// writes prior to that release are now visible on this thread.
count = mRefCount.load(std::memory_order_acquire);
#ifdef STRING_BUFFER_CANARY
mCanary = CANARY_POISON;
#endif
STRING_STAT_INCREMENT(Free);
free(this); // we were allocated with |malloc|
@@ -241,6 +260,9 @@ nsStringBuffer::Alloc(size_t aSize)
hdr->mRefCount = 1;
hdr->mStorageSize = aSize;
#ifdef STRING_BUFFER_CANARY
hdr->mCanary = CANARY_OK;
#endif
NS_LOG_ADDREF(hdr, 1, "nsStringBuffer", sizeof(*hdr));
}
return dont_AddRef(hdr);
@@ -251,6 +273,7 @@ nsStringBuffer::Realloc(nsStringBuffer* aHdr, size_t aSize)
{
STRING_STAT_INCREMENT(Realloc);
CHECK_STRING_BUFFER_CANARY(aHdr->mCanary);
NS_ASSERTION(aSize != 0, "zero capacity allocation not allowed");
NS_ASSERTION(sizeof(nsStringBuffer) + aSize <= size_t(uint32_t(-1)) &&
sizeof(nsStringBuffer) + aSize > aSize,
@@ -349,6 +372,14 @@ nsStringBuffer::SizeOfIncludingThisEvenIfShared(mozilla::MallocSizeOf aMallocSiz
return aMallocSizeOf(this);
}
#ifdef STRING_BUFFER_CANARY
void
nsStringBuffer::FromDataCanaryCheckFailed() const
{
MOZ_CRASH_UNSAFE_PRINTF("Bad canary value %d in FromData", mCanary);
}
#endif
// ---------------------------------------------------------------------------
// define nsAString