[PATCH] D73457: [Clang] Warn about 'z' printf modifier in old MSVC.

[Simon Tatham via Phabricator via cfe-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rGfe0d1b6a8ac5: [Clang] Warn about 'z' printf modifier in old MSVC. (authored by simon_tatham).

Changed prior to commit:
  https://reviews.llvm.org/D73457?vs=240626&id=240796#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D73457/new/

https://reviews.llvm.org/D73457

Files:
  clang/lib/AST/FormatString.cpp
  clang/test/Sema/format-strings-ms.c


Index: clang/test/Sema/format-strings-ms.c
===================================================================
--- clang/test/Sema/format-strings-ms.c
+++ clang/test/Sema/format-strings-ms.c
@@ -1,4 +1,6 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -fms-compatibility -triple=i386-pc-win32 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -fms-compatibility -triple=i386-pc-win32 -fms-compatibility-version=18 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -fms-compatibility -triple=i386-pc-win32 -fms-compatibility-version=19 -DSIZE_T_OK %s
 // RUN: %clang_cc1 -fsyntax-only -verify -fms-compatibility -triple=i386-pc-win32 -Wformat-non-iso -DNON_ISO_WARNING %s
 
 int printf(const char *format, ...) __attribute__((format(printf, 1, 2)));
@@ -85,4 +87,11 @@
   scanf("%Z", p); // expected-warning{{invalid conversion specifier 'Z'}}
 }
 
+void size_t_test(size_t s) {
+  printf("%zu", s);
+#ifndef SIZE_T_OK
+  // expected-warning at -2 {{length modifier 'z' results in undefined behavior or no effect with 'u' conversion specifier}}
+#endif
+}
+
 #endif
Index: clang/lib/AST/FormatString.cpp
===================================================================
--- clang/lib/AST/FormatString.cpp
+++ clang/lib/AST/FormatString.cpp
@@ -748,6 +748,15 @@
     case LengthModifier::AsIntMax:
     case LengthModifier::AsSizeT:
     case LengthModifier::AsPtrDiff:
+      if (LM.getKind() == LengthModifier::AsSizeT &&
+          Target.getTriple().isOSMSVCRT() &&
+          !LO.isCompatibleWithMSVC(LangOptions::MSVC2015)) {
+        // The standard libraries before MSVC2015 didn't support the 'z' length
+        // modifier for size_t. So if the MS compatibility version is less than
+        // that, reject.
+        return false;
+      }
+
       switch (CS.getKind()) {
         case ConversionSpecifier::dArg:
         case ConversionSpecifier::DArg:


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