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Improve zero-size allocation with safe_malloc, etc.

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Summary:
The current implementations of the memory allocation functions mistake a nullptr returned from std::malloc, std::calloc, or std::realloc as a failure. The behaviour for each of std::malloc, std::calloc, and std::realloc when the size is 0 is implementation defined (ISO/IEC 9899:2018 7.22.3), and may return a nullptr.

This patch checks if space requested is zero when a nullptr is returned, retry requesting non-zero if it is.

Authored By: andusy

Reviewers: hubert.reinterpretcast, xingxue, jasonliu

Reviewed By: hubert.reinterpretcast, xingxue, abrachet

Subscribers: abrachet, jsji, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63668

llvm-svn: 364322
This commit is contained in:
Xing Xue 2019-06-25 15:08:28 +00:00
parent 7166fad0b1
commit bbd7a470db
1 changed files with 21 additions and 3 deletions
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24
include/llvm/Support/MemAlloc.h
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@ -24,23 +24,41 @@ namespace llvm {
LLVM_ATTRIBUTE_RETURNS_NONNULL inline void *safe_malloc(size_t Sz) {
void *Result = std::malloc(Sz);
if (Result == nullptr)
if (Result == nullptr) {
// It is implementation-defined whether allocation occurs if the space
// requested is zero (ISO/IEC 9899:2018 7.22.3). Retry, requesting
// non-zero, if the space requested was zero.
if (Sz == 0)
return safe_malloc(1);
report_bad_alloc_error("Allocation failed");
}
return Result;
}
LLVM_ATTRIBUTE_RETURNS_NONNULL inline void *safe_calloc(size_t Count,
size_t Sz) {
void *Result = std::calloc(Count, Sz);
if (Result == nullptr)
if (Result == nullptr) {
// It is implementation-defined whether allocation occurs if the space
// requested is zero (ISO/IEC 9899:2018 7.22.3). Retry, requesting
// non-zero, if the space requested was zero.
if (Count == 0 || Sz == 0)
return safe_malloc(1);
report_bad_alloc_error("Allocation failed");
}
return Result;
}
LLVM_ATTRIBUTE_RETURNS_NONNULL inline void *safe_realloc(void *Ptr, size_t Sz) {
void *Result = std::realloc(Ptr, Sz);
if (Result == nullptr)
if (Result == nullptr) {
// It is implementation-defined whether allocation occurs if the space
// requested is zero (ISO/IEC 9899:2018 7.22.3). Retry, requesting
// non-zero, if the space requested was zero.
if (Sz == 0)
return safe_malloc(1);
report_bad_alloc_error("Allocation failed");
}
return Result;
}