[clang] 3e023f7 - [clang] Don't crash when -Wformat-signedness specified (#162049)

[via cfe-commits]

Author: yicuixi
Date: 2025-10-07T13:07:06+08:00
New Revision: 3e023f71692af81b7aeb31993b8b81dbd9e979f9

URL: https://github.com/llvm/llvm-project/commit/3e023f71692af81b7aeb31993b8b81dbd9e979f9
DIFF: https://github.com/llvm/llvm-project/commit/3e023f71692af81b7aeb31993b8b81dbd9e979f9.diff

LOG: [clang] Don't crash when -Wformat-signedness specified (#162049)

Fixes https://github.com/llvm/llvm-project/issues/161075. This patch
follow the changes in https://github.com/llvm/llvm-project/pull/150962,
and fix a crash issue when `-Wformat-signedness` was specificed.

Added: 
    clang/test/Sema/format-strings-signedness.cpp

Modified: 
    clang/lib/Sema/SemaChecking.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 3cc61b167ba98..063db05665af1 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -8811,8 +8811,10 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
       case ArgType::Match:
       case ArgType::MatchPromotion:
       case ArgType::NoMatchPromotionTypeConfusion:
-      case ArgType::NoMatchSignedness:
         llvm_unreachable("expected non-matching");
+      case ArgType::NoMatchSignedness:
+        Diag = diag::warn_format_conversion_argument_type_mismatch_signedness;
+        break;
       case ArgType::NoMatchPedantic:
         Diag = diag::warn_format_conversion_argument_type_mismatch_pedantic;
         break;

diff  --git a/clang/test/Sema/format-strings-signedness.cpp b/clang/test/Sema/format-strings-signedness.cpp
new file mode 100644
index 0000000000000..66bf1de1ec09a
--- /dev/null
+++ b/clang/test/Sema/format-strings-signedness.cpp
@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -verify -Wformat -Wformat-signedness %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -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 -fsyntax-only -verify -Wformat-signedness %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -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 -fsyntax-only -Wformat -verify=okay %s
+
+// Verify that -Wformat-signedness with -Wno-format are not reported (gcc compat).
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -Wformat-signedness -Wno-format -verify=okay %s
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -Wno-format -Wformat-signedness -verify=okay %s
+// okay-no-diagnostics
+
+// Ignore 'GCC requires a function with the 'format' attribute to be variadic'.
+#pragma GCC diagnostic ignored "-Wgcc-compat"
+namespace GH161075 {
+template <typename... Args>
+void format(const char *fmt, Args &&...args)
+    __attribute__((format(printf, 1, 2)));
+
+void do_format() {
+  bool b = false;
+  format("%hhi %hhu %hi %hu %i %u", b, b, b, b, b, b);  // expected-warning {{format specifies type 'unsigned char' but the argument has type 'bool', which 
diff ers in signedness}}
+}
+} // namespace GH161075