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[lldb] Add missing nullptr checks to AppleObjCRuntime::GetBacktraceThreadFromException 

Summary:
We got a few crash reports where LLDB crashes while derefencing the `frames_value` shared_ptr in the AppleObjCRuntime::GetBacktraceThreadFromException. `GetChildMemberWithName` returns a nullptr when an error occurs, so this seems to be just a missing nullptr check.

This patch adds that nullptr check and the other ones in the similar code directly below.

Fixes rdar://62174039

Reviewers: jingham, kubamracek

Reviewed By: jingham

Subscribers: abidh, JDevlieghere

Differential Revision: https://reviews.llvm.org/D78798
This commit is contained in:
Raphael Isemann 2020-05-11 16:02:17 +02:00
parent e87362e689
commit f8af9f5fca
1 changed files with 26 additions and 5 deletions
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31
lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.cpp
View File

@ -501,19 +501,32 @@ ValueObjectSP AppleObjCRuntime::GetExceptionObjectForThread(
return ValueObjectSP();
}
/// Utility method for error handling in GetBacktraceThreadFromException.
/// \param msg The message to add to the log.
/// \return An invalid ThreadSP to be returned from
/// GetBacktraceThreadFromException.
LLVM_NODISCARD
static ThreadSP FailExceptionParsing(llvm::StringRef msg) {
Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_LANGUAGE));
LLDB_LOG(log, "Failed getting backtrace from exception: {0}", msg);
return ThreadSP();
}
ThreadSP AppleObjCRuntime::GetBacktraceThreadFromException(
lldb::ValueObjectSP exception_sp) {
ValueObjectSP reserved_dict =
exception_sp->GetChildMemberWithName(ConstString("reserved"), true);
if (!reserved_dict) return ThreadSP();
if (!reserved_dict)
return FailExceptionParsing("Failed to get 'reserved' member.");
reserved_dict = reserved_dict->GetSyntheticValue();
if (!reserved_dict) return ThreadSP();
if (!reserved_dict)
return FailExceptionParsing("Failed to get synthetic value.");
TypeSystemClang *clang_ast_context =
TypeSystemClang::GetScratch(*exception_sp->GetTargetSP());
if (!clang_ast_context)
return ThreadSP();
return FailExceptionParsing("Failed to get scratch AST.");
CompilerType objc_id =
clang_ast_context->GetBasicType(lldb::eBasicTypeObjCID);
ValueObjectSP return_addresses;
@ -554,15 +567,22 @@ ThreadSP AppleObjCRuntime::GetBacktraceThreadFromException(
}
}
if (!return_addresses) return ThreadSP();
if (!return_addresses)
return FailExceptionParsing("Failed to get return addresses.");
auto frames_value =
return_addresses->GetChildMemberWithName(ConstString("_frames"), true);
if (!frames_value)
return FailExceptionParsing("Failed to get frames_value.");
addr_t frames_addr = frames_value->GetValueAsUnsigned(0);
auto count_value =
return_addresses->GetChildMemberWithName(ConstString("_cnt"), true);
if (!count_value)
return FailExceptionParsing("Failed to get count_value.");
size_t count = count_value->GetValueAsUnsigned(0);
auto ignore_value =
return_addresses->GetChildMemberWithName(ConstString("_ignore"), true);
if (!ignore_value)
return FailExceptionParsing("Failed to get ignore_value.");
size_t ignore = ignore_value->GetValueAsUnsigned(0);
size_t ptr_size = m_process->GetAddressByteSize();
@ -574,7 +594,8 @@ ThreadSP AppleObjCRuntime::GetBacktraceThreadFromException(
pcs.push_back(pc);
}
if (pcs.empty()) return ThreadSP();
if (pcs.empty())
return FailExceptionParsing("Failed to get PC list.");
ThreadSP new_thread_sp(new HistoryThread(*m_process, 0, pcs));
m_process->GetExtendedThreadList().AddThread(new_thread_sp);