FYI I changed this to early-exit again in r260563 to fix implicit builds. It’s
not safe to keep reading if we haven’t told ReadOptionsBlock to expect
failures, since it will itself early-exit, leaving the stream in the middle of
a block. It’s also a performance advantage to early exit when doing implicit
builds.
Ben
> On Jan 8, 2016, at 2:46 PM, Adrian Prantl via cfe-commits
> <cfe-commits@lists.llvm.org> wrote:
>
>>
>> On Jan 8, 2016, at 2:39 PM, Adrian Prantl <apra...@apple.com> wrote:
>>
>> Hi Richard,
>>
>> This change
>>> @@ -2239,16 +2240,21 @@ ASTReader::ReadControlBlock(ModuleFile &F,
>> [...]
>>> - if (!DisableValidation && Result != Success &&
>>> - (Result != ConfigurationMismatch ||
>>> !AllowConfigurationMismatch))
>>> + if (DisableValidation ||
>>> + (AllowConfigurationMismatch && Result ==
>>> ConfigurationMismatch))
>>> + Result = Success;
>>> +
>>> + // If we've diagnosed a problem, we're done.
>>> + if (Result != Success &&
>>> + isDiagnosedResult(Result, ClientLoadCapabilities))
>>> return Result;
>>
>> either causes or uncovers a bug:
>>
>>> CC=/Volumes/Data/llvm/_build.ninja.debug/bin/clang # r256948
>>> rm -rf cache && mkdir cache
>>> rm -rf Test && mkdir Test
>>> echo 'module Test {
>>> umbrella header "Test.h"
>>> }' >Test/module.modulemap
>>> touch Test/Test.h
>>> echo '#import <Test/Test.h>'>2.m
>>>
>>> clang -x objective-c -fmodules -fmodules-cache-path=cache -DA=0 -I. -c 2.m
>>> -o 1.o
>>> clang -x objective-c -fmodules -fmodules-cache-path=cache -Werror -DA=0 -I.
>>> -c 2.m -o 2.o
>>>
>>
>>
>> After encountering a configuration mismatch or out-of-date error, we now
>> continue instead of returning early and subsequently crash in
>>
>> ASTReader::ReadControlBlock()
>> ASTReader::getInputFile()
>> Cursor.JumpToBit(F.InputFileOffsets[ID-1]);
>>
>> I’ll keep digging deeper, but I thought you may have an intuition of what’s
>> going on here.
>> Is the behavior change intentional? From the commit message it sounds as if
>> implicit module builds shouldn’t be affected.
>
> In my particular crash isDiagnosedResult returns false for an OutOfDate
> result thus skipping the early return.
>
> -- adrian
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