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[Support/MemoryBuffer] Move the IsVolatile check inside shouldUseMmap() and make sure to zero-initialize the rest

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of the buffer if we unexpectedly reach end-of-file while reading.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208021 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Argyrios Kyrtzidis 2014-05-06 00:51:45 +00:00
parent 096d8411b3
commit 6a914399c9
1 changed files with 13 additions and 7 deletions
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20
lib/Support/MemoryBuffer.cpp
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@ -305,7 +305,14 @@ static bool shouldUseMmap(int FD,
size_t MapSize,
off_t Offset,
bool RequiresNullTerminator,
int PageSize) {
int PageSize,
bool IsVolatile) {
// mmap may leave the buffer without null terminator if the file size changed
// by the time the last page is mapped in, so avoid it if the file size is
// likely to change.
if (IsVolatile)
return false;
// We don't use mmap for small files because this can severely fragment our
// address space.
if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)
@ -381,9 +388,8 @@ static error_code getOpenFileImpl(int FD, const char *Filename,
MapSize = FileSize;
}
if (!IsVolatile &&
shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
PageSize)) {
if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
PageSize, IsVolatile)) {
error_code EC;
Result.reset(new (NamedBufferAlloc(Filename)) MemoryBufferMMapFile(
RequiresNullTerminator, FD, MapSize, Offset, EC));
@ -420,9 +426,9 @@ static error_code getOpenFileImpl(int FD, const char *Filename,
return error_code(errno, posix_category());
}
if (NumRead == 0) {
assert(0 && "We got inaccurate FileSize value or fstat reported an "
"invalid file size.");
*BufPtr = '\0'; // null-terminate at the actual size.
assert(IsVolatile && "We got inaccurate FileSize value or fstat reported "
"an invalid file size.");
memset(BufPtr, 0, BytesLeft); // zero-initialize rest of the buffer.
break;
}
BytesLeft -= NumRead;