[llvm] r271491 - [LibFuzzer] Reimplement how the optional user functions are called.

[Eric Christopher via llvm-commits]

On Sat, Jul 8, 2017 at 11:32 AM Dan Liew <dan at su-root.co.uk> wrote:

> On 8 July 2017 at 01:40, Eric Christopher <echristo at gmail.com> wrote:
> > Hi Dan,
> >
> > So this is causing warnings and breaking Werror builds:
> >
> >
> /usr/local/google/home/echristo/sources/llvm/lib/Fuzzer/FuzzerExtFunctions.def:29:10:
> > warning: ISO C++ forbids casting between pointer-to-function and
> > pointer-to-object [-Wpedantic]
> >  EXT_FUNC(__lsan_enable, void, (), false);
> >           ^
> >
> /usr/local/google/home/echristo/sources/llvm/lib/Fuzzer/FuzzerExtFunctionsWeak.cpp:44:24:
> > note: in definition of macro ‘EXT_FUNC’
> >    CheckFnPtr((void *)::NAME, #NAME, WARN);
> >                         ^
> >
> > Feel like fixing? :)
>
> Is this GCC or Clang and which version is this with?
>

Possibly gcc? And if so, quite old. :) I haven't tested with anything newer.


>
> I can think of two options to fix this.
>
> 1. Use pragmas to disable warnings in the region. E.g.
>
> ```
> #pragma GCC diagnostic push
> #pragma GCC diagnostic ignored "-Wpedantic"
>
> // do stuff
>
> #pragma GCC diagnostic pop
> ```
>
> 2. Make `CheckFnPtr a templated function so that the cast is no longer
> necessary.
>
> i.e. something like.
> ```
> template <typename T>
> static void CheckFnPtr(T FnPtr, const char *FnName, bool WarnIfMissing) {
>   if (FnPtr == nullptr && WarnIfMissing) {
>     Printf("WARNING: Failed to find function \"%s\".\n", FnName);
>   }
> }
> ```
>
> I kind of prefer option 2 but I don't like the fact this will cause us
> to emit a different implementation of `CheckFnPtr` for every single
> function signature, just so we can avoid
> a pedantic warning.
>
>
It seems like a good warning?



> @kcc: Any thoughts on this? Do you have any preferences for option 1
> or 2 or do you have an idea for a third option?
>
>
I have no preferences, but would appreciate you fixing it if possible.

Thanks

-eric
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