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Tweak implementation of -Wwrite-strings to better match the behavior of current GCCs: 

* In C, as before, if the "warning flag" is enabled, warnings are produced by
   forcing string literals to have const-qualified types (the produced warnings
   are *not* -Wwrite-strings warnings). However, more recent GCCs (at least 4.4
   onwards) now take -w into account here, so we now do the same.

 * In C++, this flag is entirely sane: it behaves just like any other warning
   flag. Stop triggering -fconst-strings here. This is a bit cleaner, but there's
   no real functionality change except in the case where -Xclang -fno-const-strings
   is also specified.

llvm-svn: 190006
This commit is contained in:
Richard Smith 2013-09-04 22:50:31 +00:00
parent 1a26927e3f
commit 282b4492db
2 changed files with 19 additions and 8 deletions
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25
clang/lib/Driver/Tools.cpp
View File

@ -2677,13 +2677,24 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
Args.AddLastArg(CmdArgs, options::OPT_trigraphs);
}
// Map the bizarre '-Wwrite-strings' flag to a more sensible
// '-fconst-strings'; this better indicates its actual behavior.
if (Args.hasFlag(options::OPT_Wwrite_strings, options::OPT_Wno_write_strings,
false)) {
// For perfect compatibility with GCC, we do this even in the presence of
// '-w'. This flag names something other than a warning for GCC.
CmdArgs.push_back("-fconst-strings");
// GCC's behavior for -Wwrite-strings is a bit strange:
// * In C, this "warning flag" changes the types of string literals from
// 'char[N]' to 'const char[N]', and thus triggers an unrelated warning
// for the discarded qualifier.
// * In C++, this is just a normal warning flag.
//
// Implementing this warning correctly in C is hard, so we follow GCC's
// behavior for now. FIXME: Directly diagnose uses of a string literal as
// a non-const char* in C, rather than using this crude hack.
if (!types::isCXX(InputType)) {
// FIXME: This should behave just like a warning flag, and thus should also
// respect -Weverything, -Wno-everything, -Werror=write-strings, and so on.
Arg *WriteStrings =
Args.getLastArg(options::OPT_Wwrite_strings,
options::OPT_Wno_write_strings, options::OPT_w);
if (WriteStrings &&
WriteStrings->getOption().matches(options::OPT_Wwrite_strings))
CmdArgs.push_back("-fconst-strings");
}
// GCC provides a macro definition '__DEPRECATED' when -Wdeprecated is active

2
clang/test/Driver/clang_f_opts.c
View File

@ -19,7 +19,7 @@
// RUN: %clang -### -S -Wwrite-strings -Wno-write-strings %s 2>&1 | FileCheck -check-prefix=WRITE-STRINGS2 %s
// WRITE-STRINGS2-NOT: -fconst-strings
// RUN: %clang -### -S -Wwrite-strings -w %s 2>&1 | FileCheck -check-prefix=WRITE-STRINGS3 %s
// WRITE-STRINGS3: -fconst-strings
// WRITE-STRINGS3-NOT: -fconst-strings
// RUN: %clang -### -x c++ -c %s 2>&1 | FileCheck -check-prefix=DEPRECATED-ON-CHECK %s
// RUN: %clang -### -x c++ -c -Wdeprecated %s 2>&1 | FileCheck -check-prefix=DEPRECATED-ON-CHECK %s