Hi,
While compiling a certain unnamed piece of mail server software, that is
a sort of mix of C99-like constructs and an extremely old K&R core, I
repeatedly received the following type of warning:
int foo(char x, int y);
int foo(x, y)
char x;
int y;
{
return x * y;
}
// $ clang -c knrpromo.c
// knrpromo.c:4:6: warning: promoted type 'int' of K&R function parameter is
not compatible with the parameter type 'char' declared in a previous prototype
// char x;
// ^
// knrpromo.c:1:14: note: previous declaration is here
// int foo(char x, int y);
// ^
// 1 warning generated.
Apparently, this is because of the promotion rules for K&R function
parameters, which are always converted to int.
While this warning is fine in itself, it cannot be turned off, which is
a nuisance, as it would be very disruptive to edit all the dozens, if
not hundreds, of prototypes and definitions in the program to fix these
cases.
Therefore, I propose the attached patch, which adds a new warning option
(-Wknr-promoted-parameter) for turning it on or off. This runs through
the standard tests just fine.
Index: tools/clang/test/Misc/warning-flags.c
===================================================================
--- tools/clang/test/Misc/warning-flags.c (revision 146850)
+++ tools/clang/test/Misc/warning-flags.c (working copy)
@@ -56,7 +56,6 @@ CHECK-NEXT: ext_missing_whitespace_after_macro_n
CHECK-NEXT: ext_new_paren_array_nonconst
CHECK-NEXT: ext_nonstandard_escape
CHECK-NEXT: ext_param_not_declared
-CHECK-NEXT: ext_param_promoted_not_compatible_with_prototype
CHECK-NEXT: ext_paste_comma
CHECK-NEXT: ext_plain_complex
CHECK-NEXT: ext_pp_bad_vaargs_use
Index: tools/clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- tools/clang/include/clang/Basic/DiagnosticSemaKinds.td (revision 146850)
+++ tools/clang/include/clang/Basic/DiagnosticSemaKinds.td (working copy)
@@ -1825,7 +1825,8 @@ def note_default_argument_declared_here : Note<
def ext_param_promoted_not_compatible_with_prototype : ExtWarn<
"promoted type %0 of K&R function parameter is not compatible with the "
- "parameter type %1 declared in a previous prototype">;
+ "parameter type %1 declared in a previous prototype">,
+ InGroup<KNRPromotedParameter>;
// C++ Overloading Semantic Analysis.
Index: tools/clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- tools/clang/include/clang/Basic/DiagnosticGroups.td (revision 146850)
+++ tools/clang/include/clang/Basic/DiagnosticGroups.td (working copy)
@@ -88,6 +88,7 @@ def LogicalOpParentheses: DiagGroup<"logical-op-pa
def IgnoredQualifiers : DiagGroup<"ignored-qualifiers">;
def : DiagGroup<"import">;
def IncompatiblePointerTypes : DiagGroup<"incompatible-pointer-types">;
+def KNRPromotedParameter : DiagGroup<"knr-promoted-parameter">;
def : DiagGroup<"init-self">;
def : DiagGroup<"inline">;
def : DiagGroup<"int-to-pointer-cast">;
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