[PATCH] D122895: [C89/C2x] Improve diagnostics around strict prototypes in C

[Eli Friedman via Phabricator via cfe-commits]

efriedma added inline comments.


================
Comment at: clang/test/Sema/warn-strict-prototypes.m:20
+  // know it's a block when diagnosing.
+  void (^block2)(void) = ^void() { // expected-warning {{a function declaration without a prototype is deprecated in all versions of C}}
   };
----------------
dexonsmith wrote:
> dexonsmith wrote:
> > This is a definition, so the compiler knows that there are no parameters. Why would we warn here? Reading https://discourse.llvm.org/t/rfc-enabling-wstrict-prototypes-by-default-in-c/60521/18 it looks to me like an example of what @rnk was referring to, about churning code to add `(void)` and then return back to `()` later.
> > 
> > (cc: @steven_wu and @rjmccall as well)
> Specifically, `^void() { /* anything */}` is the definition of a block with zero parameters. Maybe pedantically it's lacking a prototype, but the compiler knows (since this is the definition) how many parameters there are.
> 
> (Same goes for `void() { /* anything */ }` at global scope; is that triggering `-Wstrict-prototypes` now too?)
To be clear, you're asking specifically about the following two cases where the behavior with -Wstrict-prototypes changed, right?  I don't think this was really discussed in the RFC.

```
// Block
void (^f1)(void) = ^(){};

// Function definition
void f(void);
void f(){}
```

Note that the behavior of the following did not change:

```
void (^f1)(void) = ^{}; // no warning
void f2(){} // warning since clang 11.
```


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  https://reviews.llvm.org/D122895/new/

https://reviews.llvm.org/D122895