Add support for -Wwrite-strings. Patch by Mike M! Fixes PR 4804.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@98541 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/LangOptions.h

@@ -44,6 +44,7 @@ public:
 
   unsigned PascalStrings     : 1;  // Allow Pascal strings
   unsigned WritableStrings   : 1;  // Allow writable strings
+  unsigned ConstStrings      : 1;  // Add const qualifier to strings (-Wwrite-strings)
   unsigned LaxVectorConversions : 1;
   unsigned AltiVec           : 1;  // Support AltiVec-style vector initializers.
   unsigned Exceptions        : 1;  // Support exception handling.
@@ -129,7 +130,7 @@ public:
     HexFloats = 0;
     GC = ObjC1 = ObjC2 = ObjCNonFragileABI = ObjCNonFragileABI2 = 0;
     C99 = Microsoft = CPlusPlus = CPlusPlus0x = 0;
-    CXXOperatorNames = PascalStrings = WritableStrings = 0;
+    CXXOperatorNames = PascalStrings = WritableStrings = ConstStrings = 0;
     Exceptions = SjLjExceptions = Freestanding = NoBuiltin = 0;
     NeXTRuntime = 1;
     RTTI = 1;

include/clang/Driver/CC1Options.td

@@ -197,6 +197,8 @@ def fcolor_diagnostics : Flag<"-fcolor-diagnostics">,
   HelpText<"Use colors in diagnostics">;
 def Wno_rewrite_macros : Flag<"-Wno-rewrite-macros">,
   HelpText<"Silence ObjC rewriting warnings">;
+def Wwrite_strings : Flag<"-Wwrite-strings">,
+  HelpText<"Add const qualifier to string literals">;
 def verify : Flag<"-verify">,
   HelpText<"Verify emitted diagnostics and warnings">;
 

lib/Frontend/CompilerInvocation.cpp

@@ -474,6 +474,8 @@ static void LangOptsToArgs(const LangOptions &Opts,
     Res.push_back("-fcatch-undefined-behavior");
   if (Opts.WritableStrings)
     Res.push_back("-fwritable-strings");
+  if (Opts.ConstStrings)
+    Res.push_back("-Wwrite-strings");
   if (!Opts.LaxVectorConversions)
     Res.push_back("-fno-lax-vector-conversions");
   if (Opts.AltiVec)
@@ -1162,6 +1164,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args,
   Opts.PascalStrings = Args.hasArg(OPT_fpascal_strings);
   Opts.Microsoft = Args.hasArg(OPT_fms_extensions);
   Opts.WritableStrings = Args.hasArg(OPT_fwritable_strings);
+  Opts.ConstStrings = Args.hasArg(OPT_Wwrite_strings);
   if (Args.hasArg(OPT_fno_lax_vector_conversions))
     Opts.LaxVectorConversions = 0;
   if (Args.hasArg(OPT_fno_threadsafe_statics))

lib/Sema/SemaExpr.cpp

@@ -370,7 +370,7 @@ Sema::ActOnStringLiteral(const Token *StringToks, unsigned NumStringToks) {
   if (Literal.Pascal) StrTy = Context.UnsignedCharTy;
 
   // A C++ string literal has a const-qualified element type (C++ 2.13.4p1).
-  if (getLangOptions().CPlusPlus)
+  if (getLangOptions().CPlusPlus || getLangOptions().ConstStrings )
     StrTy.addConst();
 
   // Get an array type for the string, according to C99 6.4.5.  This includes

lib/Sema/SemaExprObjC.cpp

@@ -106,7 +106,7 @@ Expr *Sema::BuildObjCEncodeExpression(SourceLocation AtLoc,
     // which is an array type.
     StrTy = Context.CharTy;
     // A C++ string literal has a const-qualified element type (C++ 2.13.4p1).
-    if (getLangOptions().CPlusPlus)
+    if (getLangOptions().CPlusPlus || getLangOptions().ConstStrings)
       StrTy.addConst();
     StrTy = Context.getConstantArrayType(StrTy, llvm::APInt(32, Str.size()+1),
                                          ArrayType::Normal, 0);

test/Sema/warn-write-strings.c

@@ -0,0 +1,4 @@
+// RUN: %clang_cc1 -verify -fsyntax-only -Wwrite-strings %s
+
+// PR4804
+char* x = "foo"; // expected-warning {{initializing 'char const [4]' discards qualifiers, expected 'char *'}}

test/SemaObjC/warn-write-strings.m

@@ -0,0 +1,4 @@
+// RUN: %clang_cc1 -verify -fsyntax-only -Wwrite-strings %s
+
+// PR4804
+char* x = "foo"; // expected-warning {{initializing 'char const [4]' discards qualifiers, expected 'char *'}}