Index: include/clang/Basic/DiagnosticSemaKinds.td =================================================================== --- include/clang/Basic/DiagnosticSemaKinds.td +++ include/clang/Basic/DiagnosticSemaKinds.td @@ -4129,6 +4129,10 @@ InGroup>, DefaultIgnore; def note_declaration_not_a_prototype : Note< "this declaration is not a prototype; add 'void' to make it a prototype for a zero-parameter function">; +def warn_strict_prototypes : Warning< + "this %select{function declaration is not|" + "old-style function definition is not preceded by}0 a prototype">, + InGroup>, DefaultIgnore; def warn_missing_variable_declarations : Warning< "no previous extern declaration for non-static variable %0">, InGroup>, DefaultIgnore; Index: lib/Sema/SemaDecl.cpp =================================================================== --- lib/Sema/SemaDecl.cpp +++ lib/Sema/SemaDecl.cpp @@ -11160,6 +11160,22 @@ << FixItHint::CreateInsertion(FTL.getRParenLoc(), "void"); } } + + // GNU warning -Wstrict-prototypes + // Warn if K&R function is defined without previous declaration + // declaration. This warning is issued only if the difinition itself + // does not provide a prototype. Only K&R definitions do not + // provide a prototype. + // An empty list in a function declarator that is part of a definition + // of that function specifies that the function has no parameters + // (C99 6.7.5.3p14) + if (!FD->hasWrittenPrototype() && FD->getNumParams() > 0 && + !LangOpts.CPlusPlus) { + TypeSourceInfo* TI = FD->getTypeSourceInfo(); + TypeLoc TL = TI->getTypeLoc(); + FunctionTypeLoc FTL = TL.castAs(); + Diag(FTL.getLParenLoc(), diag::warn_strict_prototypes) << 1; + } } if (auto *MD = dyn_cast(FD)) { Index: lib/Sema/SemaType.cpp =================================================================== --- lib/Sema/SemaType.cpp +++ lib/Sema/SemaType.cpp @@ -3919,6 +3919,20 @@ if (FTI.isAmbiguous) warnAboutAmbiguousFunction(S, D, DeclType, T); + // GNU warning -Wstrict-prototypes + // Warn if function declaration is without prototype. + // This warning is issued for all kinds of unprototyped function + // declarations (i.e. function type typedef, function pointer etc.) + // C99 6.7.5.3p14: + // The empty list in a function declarator that is not part of a + // definition of that function specifies that no information + // about the number or types of the parameters is supplied. + if (D.getFunctionDefinitionKind() == FDK_Declaration && + FTI.NumParams == 0 && !LangOpts.CPlusPlus) { + S.Diag(DeclType.Loc, diag::warn_strict_prototypes) << 0 + << FixItHint::CreateInsertion(FTI.getRParenLoc(), "void"); + } + FunctionType::ExtInfo EI(getCCForDeclaratorChunk(S, D, FTI, chunkIndex)); if (!FTI.NumParams && !FTI.isVariadic && !LangOpts.CPlusPlus) { Index: test/Sema/warn-strict-prototypes.c =================================================================== --- test/Sema/warn-strict-prototypes.c +++ test/Sema/warn-strict-prototypes.c @@ -0,0 +1,78 @@ +// RUN: %clang_cc1 -fsyntax-only -Wstrict-prototypes -verify %s +// RUN: %clang_cc1 -fsyntax-only -Wstrict-prototypes -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s + +// function declaration with unspecified params +void foo1(); // expected-warning{{this function declaration is not a prototype}} + // CHECK: fix-it:"{{.*}}":{5:11-5:11}:"void" +// function declaration with 0 params +void foo2(void); + +// function definition with 0 params(for both cases), valid according to 6.7.5.3/14 +void foo1() {} +void foo2(void) {} + +// function type typedef unspecified params +typedef void foo3(); // expected-warning{{this function declaration is not a prototype}} + // CHECK: fix-it:"{{.*}}":{15:19-15:19}:"void" +void bar1(void) { + foo3 *fp = 0; + (*fp)(); +} + +// global fp unspecified params +void (*foo4)(); // expected-warning{{this function declaration is not a prototype}} + // CHECK: fix-it:"{{.*}}":{23:14-23:14}:"void" + +// struct member fp unspecified params +struct { void (*foo5)(); } s; // expected-warning{{this function declaration is not a prototype}} + // CHECK: fix-it:"{{.*}}":{27:23-27:23}:"void" + +// param fp unspecified params +void bar2(void (*foo6)()) { // expected-warning{{this function declaration is not a prototype}} + // CHECK: fix-it:"{{.*}}":{31:24-31:24}:"void" + // local fp unspecified params + void (*foo7)() = 0; // expected-warning{{this function declaration is not a prototype}} + // CHECK: fix-it:"{{.*}}":{34:16-34:16}:"void" + // array fp unspecified params + void (*foo8[2])() = {0}; // expected-warning{{this function declaration is not a prototype}} + // CHECK: fix-it:"{{.*}}":{37:19-37:19}:"void" + // use them + foo4(); + s.foo5(); + foo6(); + foo7(); + foo8[0](); +} + +// function type cast using using an anonymous function declaration +void bar3(int a) { + // casting function w/out prototype to unspecified params function type + (void)(void(*)()) foo1; // expected-warning{{this function declaration is not a prototype}} + // CHECK: fix-it:"{{.*}}":{50:18-50:18}:"void" + // .. specified params + (void)(void(*)(void)) foo1; + + // casting function w/ prototype to unspecified params function type + (void)(void(*)()) foo2; // expected-warning{{this function declaration is not a prototype}} + // CHECK: fix-it:"{{.*}}":{56:18-56:18}:"void" + // .. specified params + (void)(void(*)(void)) foo2; +} + +// K&R function definition not preceded by full prototype +int foo9(a, b) // expected-warning{{old-style function definition is not preceded by a prototype}} + int a, b; +{ + return a + b; +} + +// Function declaration with no types +void foo10(); // expected-warning{{this function declaration is not a prototype}} + // CHECK: fix-it:"{{.*}}":{70:12-70:12}:"void" +// K&R function definition with incomplete param list declared +void foo10(p, p2) void *p; {} // expected-warning{{old-style function definition is not preceded by a prototype}} + +// Prototype declaration +void foo11(int p, int p2); +// K&R function definition with previous prototype declared is not diagnosed. +void foo11(p, p2) int p; int p2; {}