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ExceptionDemo: remove some undefined behaviour

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The casting based reading of the LSDA could attempt to read unsuitably aligned
data.  Avoid that case by explicitly using a memcpy.  A similar approach is used
in libc++abi to address the same UB.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@287479 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Saleem Abdulrasool 2016-11-20 02:36:38 +00:00
parent 308b046dd4
commit 802a1be56a
1 changed files with 17 additions and 14 deletions
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31
examples/ExceptionDemo/ExceptionDemo.cpp
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@ -219,6 +219,16 @@ static llvm::AllocaInst *createEntryBlockAlloca(llvm::Function &function,
// Runtime C Library functions
//
namespace {
template <typename Type_>
uintptr_t ReadType(const uint8_t *&p) {
Type_ value;
memcpy(&value, p, sizeof(Type_));
p += sizeof(Type_);
return static_cast<uintptr_t>(value);
}
}
// Note: using an extern "C" block so that static functions can be used
extern "C" {
@ -409,8 +419,7 @@ static uintptr_t readEncodedPointer(const uint8_t **data, uint8_t encoding) {
// first get value
switch (encoding & 0x0F) {
case llvm::dwarf::DW_EH_PE_absptr:
result = *((uintptr_t*)p);
p += sizeof(uintptr_t);
result = ReadType<uintptr_t>(p);
break;
case llvm::dwarf::DW_EH_PE_uleb128:
result = readULEB128(&p);
@ -420,28 +429,22 @@ static uintptr_t readEncodedPointer(const uint8_t **data, uint8_t encoding) {
result = readSLEB128(&p);
break;
case llvm::dwarf::DW_EH_PE_udata2:
result = *((uint16_t*)p);
p += sizeof(uint16_t);
result = ReadType<uint16_t>(p);
break;
case llvm::dwarf::DW_EH_PE_udata4:
result = *((uint32_t*)p);
p += sizeof(uint32_t);
result = ReadType<uint32_t>(p);
break;
case llvm::dwarf::DW_EH_PE_udata8:
result = *((uint64_t*)p);
p += sizeof(uint64_t);
result = ReadType<uint64_t>(p);
break;
case llvm::dwarf::DW_EH_PE_sdata2:
result = *((int16_t*)p);
p += sizeof(int16_t);
result = ReadType<int16_t>(p);
break;
case llvm::dwarf::DW_EH_PE_sdata4:
result = *((int32_t*)p);
p += sizeof(int32_t);
result = ReadType<int32_t>(p);
break;
case llvm::dwarf::DW_EH_PE_sdata8:
result = *((int64_t*)p);
p += sizeof(int64_t);
result = ReadType<int64_t>(p);
break;
default:
// not supported