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

[Justin Bogner]

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 &".

> +    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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