[llvm] r236741 - Fix another hang caused by ManagedStatic in SignalHandler

[Steven Wu]

> On May 7, 2015, at 11:29 AM, Justin Bogner <mail at justinbogner.com> wrote:
> 
> Steven Wu <stevenwu at apple.com> writes:
>> Author: steven_wu
>> Date: Thu May  7 11:20:51 2015
>> New Revision: 236741
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=236741&view=rev
>> Log:
>> Fix another hang caused by ManagedStatic in SignalHandler
>> 
>> Fix two other variables that might cause the same hang fixed in r235914.
>> The hang is caused by constructing ManagedStatic in signalhandler. In
>> this case, if FileToRemove or CallBacksToRun is not contructed, it means
>> there is no work to do.
>> 
>> Modified:
>>    llvm/trunk/lib/Support/Unix/Signals.inc
>> 
>> Modified: llvm/trunk/lib/Support/Unix/Signals.inc
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Unix/Signals.inc?rev=236741&r1=236740&r2=236741&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Support/Unix/Signals.inc (original)
>> +++ llvm/trunk/lib/Support/Unix/Signals.inc Thu May  7 11:20:51 2015
>> @@ -139,6 +139,11 @@ static void UnregisterHandlers() {
>> /// NB: This must be an async signal safe function. It cannot allocate or free
>> /// memory, even in debug builds.
>> static void RemoveFilesToRemove() {
>> +  // Avoid constructing ManagedStatic in the signal handler.
>> +  // If FilesToRemove is not constructed, there are no files to remove.
>> +  if (!FilesToRemove.isConstructed())
>> +    return;
>> +
>>   // We avoid iterators in case of debug iterators that allocate or release
>>   // memory.
>>   std::vector<std::string>& FilesToRemoveRef = *FilesToRemove;
>> @@ -200,10 +205,12 @@ static RETSIGTYPE SignalHandler(int Sig)
>>   }
>> 
>>   // Otherwise if it is a fault (like SEGV) run any handler.
>> -  std::vector<std::pair<void (*)(void *), void *>>& CallBacksToRunRef =
>> -      *CallBacksToRun;
>> -  for (unsigned i = 0, e = CallBacksToRun->size(); i != e; ++i)
>> -    CallBacksToRunRef[i].first(CallBacksToRunRef[i].second);
>> +  if (CallBacksToRun.isConstructed()) {
>> +    std::vector<std::pair<void (*)(void *), void *>>& CallBacksToRunRef =
>> +        *CallBacksToRun;
> 
> This looks like a job for "auto &”.
Ok. Agree. Commit in r236768.

> 
>> +    for (unsigned i = 0, e = CallBacksToRun->size(); i != e; ++i)
>> +      CallBacksToRunRef[i].first(CallBacksToRunRef[i].second);
>> +  }
>> 
>> #ifdef __s390__
>>   // On S/390, certain signals are delivered with PSW Address pointing to
>> 
>> 
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