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[Support] Fix error handling in DataExtractor::get[US]LEB128 

Summary:
These functions are documented as not modifying the offset argument if
the extraction fails (just like other DataExtractor functions). However,
while reviewing D63591 we discovered that this is not the case -- if the
function reaches the end of the data buffer, it will just return the
value parsed until that point and set offset to point to the end of the
buffer.

This fixes the functions to act as advertised, and adds a regression
test.

Reviewers: dblaikie, probinson, bkramer

Subscribers: kristina, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63645

llvm-svn: 364169
This commit is contained in:
Pavel Labath 2019-06-24 09:11:24 +00:00
parent a94c18fc20
commit bb6d0b8e7b
2 changed files with 24 additions and 14 deletions
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28
llvm/lib/Support/DataExtractor.cpp
View File

@ -157,12 +157,12 @@ uint64_t DataExtractor::getULEB128(uint32_t *offset_ptr) const {
byte = Data[offset++];
result |= uint64_t(byte & 0x7f) << shift;
shift += 7;
if ((byte & 0x80) == 0)
break;
if ((byte & 0x80) == 0) {
*offset_ptr = offset;
return result;
}
}
*offset_ptr = offset;
return result;
return 0;
}
int64_t DataExtractor::getSLEB128(uint32_t *offset_ptr) const {
@ -178,14 +178,14 @@ int64_t DataExtractor::getSLEB128(uint32_t *offset_ptr) const {
byte = Data[offset++];
result |= uint64_t(byte & 0x7f) << shift;
shift += 7;
if ((byte & 0x80) == 0)
break;
if ((byte & 0x80) == 0) {
// Sign bit of byte is 2nd high order bit (0x40)
if (shift < 64 && (byte & 0x40))
result |= -(1ULL << shift);
*offset_ptr = offset;
return result;
}
}
// Sign bit of byte is 2nd high order bit (0x40)
if (shift < 64 && (byte & 0x40))
result |= -(1ULL << shift);
*offset_ptr = offset;
return result;
return 0;
}

10
llvm/unittests/Support/DataExtractorTest.cpp
View File

@ -116,4 +116,14 @@ TEST(DataExtractorTest, LEB128) {
EXPECT_EQ(8U, offset);
}
TEST(DataExtractorTest, LEB128_error) {
DataExtractor DE(StringRef("\x81"), false, 8);
uint32_t Offset = 0;
EXPECT_EQ(0U, DE.getULEB128(&Offset));
EXPECT_EQ(0U, Offset);
Offset = 0;
EXPECT_EQ(0U, DE.getSLEB128(&Offset));
EXPECT_EQ(0U, Offset);
}
}