From f7e7fdd5cfebf4a8a30e4b4dce410a237f13a17c Mon Sep 17 00:00:00 2001 From: Pavel Labath Date: Tue, 26 Jul 2016 08:11:57 +0000 Subject: [PATCH] Fix DataExtractor::PeekData for zero length peeks Summary: The function was returning the null pointer for peeks of size zero, which seems like a sensible thing to do, but is actually pretty easy to get bitten by that if you are extracting a variable length field which happens to be of zero length and then doing pointer arithmetic on that (which SymbolFileDWARF does, and ended up crashing in case of empty DW_AT_location). This changes the function to return a null pointer only when it gets queried for data which is outside of the range of the extractor, which is more c++-y, as one can still do reasonable things with pointers to data of size zero (think, end() iterators). I also add a test and fix some signedness warnings in the existing data extractor tests. Reviewers: clayborg Subscribers: lldb-commits Differential Revision: https://reviews.llvm.org/D22755 llvm-svn: 276734 --- lldb/include/lldb/Core/DataExtractor.h | 2 +- lldb/unittests/Core/DataExtractorTest.cpp | 23 ++++++++++++++++++++--- 2 files changed, 21 insertions(+), 4 deletions(-) diff --git a/lldb/include/lldb/Core/DataExtractor.h b/lldb/include/lldb/Core/DataExtractor.h index 51ecade..8fbdb692 100644 --- a/lldb/include/lldb/Core/DataExtractor.h +++ b/lldb/include/lldb/Core/DataExtractor.h @@ -1139,7 +1139,7 @@ public: const uint8_t* PeekData (lldb::offset_t offset, lldb::offset_t length) const { - if (length > 0 && ValidOffsetForDataOfSize(offset, length)) + if (ValidOffsetForDataOfSize(offset, length)) return m_start + offset; return nullptr; } diff --git a/lldb/unittests/Core/DataExtractorTest.cpp b/lldb/unittests/Core/DataExtractorTest.cpp index f228838..22438e5 100644 --- a/lldb/unittests/Core/DataExtractorTest.cpp +++ b/lldb/unittests/Core/DataExtractorTest.cpp @@ -21,7 +21,7 @@ using namespace lldb_private; TEST(DataExtractorTest, GetBitfield) { - char buffer[] = { 0x01, 0x23, 0x45, 0x67 }; + uint8_t buffer[] = { 0x01, 0x23, 0x45, 0x67 }; DataExtractor LE(buffer, sizeof(buffer), lldb::eByteOrderLittle, sizeof(void *)); DataExtractor BE(buffer, sizeof(buffer), lldb::eByteOrderBig, sizeof(void *)); @@ -33,7 +33,24 @@ TEST(DataExtractorTest, GetBitfield) ASSERT_EQ(buffer[1], BE.GetMaxU64Bitfield(&offset, sizeof(buffer), 8, 8)); offset = 0; - ASSERT_EQ(buffer[1], LE.GetMaxS64Bitfield(&offset, sizeof(buffer), 8, 8)); + ASSERT_EQ(int8_t(buffer[1]), LE.GetMaxS64Bitfield(&offset, sizeof(buffer), 8, 8)); offset = 0; - ASSERT_EQ(buffer[1], BE.GetMaxS64Bitfield(&offset, sizeof(buffer), 8, 8)); + ASSERT_EQ(int8_t(buffer[1]), BE.GetMaxS64Bitfield(&offset, sizeof(buffer), 8, 8)); +} + +TEST(DataExtractorTest, PeekData) +{ + uint8_t buffer[] = { 0x01, 0x02, 0x03, 0x04 }; + DataExtractor E(buffer, sizeof buffer, lldb::eByteOrderLittle, 4); + + EXPECT_EQ(buffer + 0, E.PeekData(0, 0)); + EXPECT_EQ(buffer + 0, E.PeekData(0, 4)); + EXPECT_EQ(nullptr, E.PeekData(0, 5)); + + EXPECT_EQ(buffer + 2, E.PeekData(2, 0)); + EXPECT_EQ(buffer + 2, E.PeekData(2, 2)); + EXPECT_EQ(nullptr, E.PeekData(2, 3)); + + EXPECT_EQ(buffer + 4, E.PeekData(4, 0)); + EXPECT_EQ(nullptr, E.PeekData(4, 1)); } -- 2.7.4