[Coverage] Ensure that coverage mapping data has an expected alignment in 'covmapping' files.

Coverage mapping data is organized in a sequence of blocks, each of which is expected
to be aligned by 8 bytes. This feature is used when reading those blocks, see
VersionedCovMapFuncRecordReader::readFunctionRecords(). If a misaligned covearge
mapping data has more than one block, it causes llvm-cov to fail.

Differential Revision: http://reviews.llvm.org/D20285

llvm-svn: 269887

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/tools/llvm-cov/TestingSupport.cpp b/llvm/tools/llvm-cov/TestingSupport.cpp
index f6c91f85c84..a662a155255 100644
--- a/llvm/tools/llvm-cov/TestingSupport.cpp
+++ b/llvm/tools/llvm-cov/TestingSupport.cpp
@@ -88,7 +88,11 @@ int convertForTestingMain(int argc, const char *argv[]) {
   OS << "llvmcovmtestdata";
   encodeULEB128(ProfileNamesData.size(), OS);
   encodeULEB128(ProfileNamesAddress, OS);
-  OS << ProfileNamesData << CoverageMappingData;
+  OS << ProfileNamesData;
+  // Coverage mapping data is expected to have an alignment of 8.
+  for (unsigned Pad = OffsetToAlignment(OS.tell(), 8); Pad; --Pad)
+    OS.write(uint8_t(0));
+  OS << CoverageMappingData;
 
   return 0;
 }