[clang] [llvm] [Sema] Implement support for -Wformat-signedness (PR #74440)

[Aaron Ballman via cfe-commits]

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@@ -0,0 +1,223 @@
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -verify -Wformat -Wformat-signedness %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -std=c11 -fsyntax-only -verify -Wformat -Wformat-signedness %s
+
+// Verify that -Wformat-signedness alone (without -Wformat) trigger the
+// warnings. Note in gcc this will not trigger the signedness warnings as
+// -Wformat is default off in gcc.
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -verify -Wformat-signedness %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -std=c11 -fsyntax-only -verify -Wformat-signedness %s
+
+// Verify that -Wformat-signedness warnings are not reported with only -Wformat
+// (gcc compat).
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -Wformat -Werror %s
+
+// Verify that -Wformat-signedness with -Wno-format are not reported (gcc compat).
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -Wformat-signedness -Wno-format -Werror %s
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -Wno-format -Wformat-signedness -Werror %s
----------------
AaronBallman wrote:

```suggestion
// Verify that -Wformat-signedness warnings are not reported with only -Wformat
// (gcc compat).
// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -Wformat -Werror %s

// Verify that -Wformat-signedness with -Wno-format are not reported (gcc compat).
// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -Wformat-signedness -Wno-format -verify=okay %s
// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -Wno-format -Wformat-signedness -verify=okay %s

// okay-no-diagnostics
```
These are all missing `-verify` lines so they're relying on `-Werror` to upgrade diagnostics from warnings to errors and that the return value from `clang -cc1` will be non-zero if a diagnostic was emitted. This works but is a bit subtle -- usually we'd have `-verify` in all of the `RUN` lines and we'd use a different prefix for these and we ensure there are no diagnostics with the diagnostics verifier, along these lines.

https://github.com/llvm/llvm-project/pull/74440