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.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190006 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 524247f..dd72fd7 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -2677,13 +2677,24 @@
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