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[lldb] Skip null bytes in embedded type summaries #8132

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Merged
merged 1 commit into from
Feb 8, 2024
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[lldb] Skip null bytes in embedded type summaries #8132

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18 changes: 18 additions & 0 deletions lldb/source/Target/Target.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1476,8 +1476,26 @@ static void LoadTypeSummariesForModule(ModuleSP module_sp) {
auto section_size = summaries_sp->GetSectionData(extractor);
lldb::offset_t offset = 0;
while (offset < section_size) {
// Skip null bytes. Can happen with alignment padding.
while (true) {
auto next_offset = offset;
if (extractor.GetU8(&next_offset) != 0) {
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Why is next_offset needed? Does GetU8 modify the parameter in the failure case?

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yes, the passed in offset is an in-out parameter. As far as GetU8 is concerned, reading a zero byte is not a failure case. If there was a PeekU8 method that would be better suited.

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open to suggestions

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No this is fine. I misread the condition, as checking for an error, but it's checking for the NUL byte.

break;
}
// Move past the null byte, using the advanced offset.
offset = next_offset;
}

uint64_t version = extractor.GetULEB128(&offset);
uint64_t record_size = extractor.GetULEB128(&offset);
if (record_size == 0) {
LLDB_LOGF(log,
"Skipping empty (malformed) embedded type summary of version "
"%llu in %s.",
version, module_name);
continue;
}

if (version == 1) {
uint64_t type_size = extractor.GetULEB128(&offset);
llvm::StringRef type_name = extractor.GetCStr(&offset, type_size);
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6 changes: 2 additions & 4 deletions lldb/test/API/functionalities/data-formatter/embedded-summary/main.c
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Expand Up @@ -5,8 +5,7 @@ struct Player {
int number;
};

__attribute__((aligned(1), used,
section("__DATA_CONST,__lldbsummaries"))) unsigned char
__attribute__((used, section("__DATA_CONST,__lldbsummaries"))) unsigned char
_Player_type_summary[] = "\x01" // version
"\x25" // record size
"\x07" // type name size
Expand All @@ -20,8 +19,7 @@ struct Layer {
};

// Near copy of the record for `Player`, using a regex type name (`^Layer`).
__attribute__((aligned(1), used,
section("__DATA_CONST,__lldbsummaries"))) unsigned char
__attribute__((used, section("__DATA_CONST,__lldbsummaries"))) unsigned char
_Layer_type_summary[] = "\x01" // version
"\x25" // record size
"\x07" // type name size
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