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Improve the strict prototype diagnostic behavior

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Post-commit feedback on https://reviews.llvm.org/D122895 pointed out
that the diagnostic wording for some code was using "declaration" in a
confusing way, such as:

int foo(); // warning: a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x

int foo(int arg) { // warning: a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x
  return 5;
}

And that we had other minor issues with the diagnostics being somewhat
confusing.

This patch addresses the confusion by reworking the implementation to
be a bit more simple and a bit less chatty. Specifically, it changes
the warning and note diagnostics to be able to specify "declaration" or
"definition" as appropriate, and it changes the function merging logic
so that the function without a prototype is always what gets warned on,
and the function with a prototype is sometimes what gets noted.
Additionally, when diagnosing a K&R C definition that is preceded by a
function without a prototype, we don't note the prior declaration, we
warn on it because it will also be changing behavior in C2x.

Differential Revision: https://reviews.llvm.org/D125814
This commit is contained in:
Aaron Ballman 2022-05-26 07:52:19 -04:00
parent cd5783d3e8
commit 681c50c62e
10 changed files with 77 additions and 122 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
clang/include/clang/Basic/DiagnosticSemaKinds.td
View File

@ -5589,10 +5589,12 @@ def warn_strict_prototypes : Extension<
"a %select{function|block}0 declaration without a prototype is deprecated "
"%select{in all versions of C|}0">, InGroup<StrictPrototypes>;
def warn_non_prototype_changes_behavior : Warning<
"a function declaration without a prototype is deprecated in all versions of "
"C and is not supported in C2x">, InGroup<DeprecatedNonPrototype>;
def note_func_decl_changes_behavior : Note<
"a function declaration without a prototype is not supported in C2x">;
"a function %select{declaration|definition}0 without a prototype is "
"deprecated in all versions of C %select{and is not supported in C2x|and is "
"treated as a zero-parameter prototype in C2x, conflicting with a "
"%select{previous|subsequent}2 %select{declaration|definition}3}1">,
InGroup<DeprecatedNonPrototype>;
def note_conflicting_prototype : Note<"conflicting prototype is here">;
def warn_missing_variable_declarations : Warning<
"no previous extern declaration for non-static variable %0">,
InGroup<DiagGroup<"missing-variable-declarations">>, DefaultIgnore;

107
clang/lib/Sema/SemaDecl.cpp
View File

@ -3940,59 +3940,29 @@ bool Sema::MergeFunctionDecl(FunctionDecl *New, NamedDecl *&OldD, Scope *S,
}
if (WithProto->getNumParams() != 0) {
// The function definition has parameters, so this will change
// behavior in C2x.
//
// If we already warned about about the function without a prototype
// being deprecated, add a note that it also changes behavior. If we
// didn't warn about it being deprecated (because the diagnostic is
// not enabled), warn now that it is deprecated and changes behavior.
bool AddNote = false;
if (Diags.isIgnored(diag::warn_strict_prototypes,
WithoutProto->getLocation())) {
if (WithoutProto->getBuiltinID() == 0 &&
!WithoutProto->isImplicit() &&
SourceMgr.isBeforeInTranslationUnit(WithoutProto->getLocation(),
WithProto->getLocation())) {
PartialDiagnostic PD =
PDiag(diag::warn_non_prototype_changes_behavior);
if (TypeSourceInfo *TSI = WithoutProto->getTypeSourceInfo()) {
if (auto FTL = TSI->getTypeLoc().getAs<FunctionNoProtoTypeLoc>())
PD << FixItHint::CreateInsertion(FTL.getRParenLoc(), "void");
}
Diag(WithoutProto->getLocation(), PD);
}
} else {
AddNote = true;
}
// Because the function with a prototype has parameters but a previous
// declaration had none, the function with the prototype will also
// change behavior in C2x.
if (WithProto->getBuiltinID() == 0 && !WithProto->isImplicit()) {
if (SourceMgr.isBeforeInTranslationUnit(
WithProto->getLocation(), WithoutProto->getLocation())) {
// If the function with the prototype comes before the function
// without the prototype, we only want to diagnose the one without
// the prototype.
Diag(WithoutProto->getLocation(),
diag::warn_non_prototype_changes_behavior);
} else {
// Otherwise, diagnose the one with the prototype, and potentially
// attach a note to the one without a prototype if needed.
Diag(WithProto->getLocation(),
diag::warn_non_prototype_changes_behavior);
if (AddNote && WithoutProto->getBuiltinID() == 0)
Diag(WithoutProto->getLocation(),
diag::note_func_decl_changes_behavior);
}
} else if (AddNote && WithoutProto->getBuiltinID() == 0 &&
!WithoutProto->isImplicit()) {
// If we were supposed to add a note but the function with a
// prototype is a builtin or was implicitly declared, which means we
// have nothing to attach the note to, so we issue a warning instead.
if (WithoutProto->getBuiltinID() == 0 && !WithoutProto->isImplicit()) {
// The one without the prototype will be changing behavior in C2x, so
// warn about that one so long as it's a user-visible declaration.
bool IsWithoutProtoADef = false, IsWithProtoADef = false;
if (WithoutProto == New)
IsWithoutProtoADef = NewDeclIsDefn;
else
IsWithProtoADef = NewDeclIsDefn;
Diag(WithoutProto->getLocation(),
diag::warn_non_prototype_changes_behavior);
diag::warn_non_prototype_changes_behavior)
<< IsWithoutProtoADef << (WithoutProto->getNumParams() ? 0 : 1)
<< (WithoutProto == Old) << IsWithProtoADef;
// The reason the one without the prototype will be changing behavior
// is because of the one with the prototype, so note that so long as
// it's a user-visible declaration. There is one exception to this:
// when the new declaration is a definition without a prototype, the
// old declaration with a prototype is not the cause of the issue,
// and that does not need to be noted because the one with a
// prototype will not change behavior in C2x.
if (WithProto->getBuiltinID() == 0 && !WithProto->isImplicit() &&
!IsWithoutProtoADef)
Diag(WithProto->getLocation(), diag::note_conflicting_prototype);
}
}
}
@ -15053,29 +15023,22 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
// deprecated, add a note that it also changes behavior. If we didn't
// warn about it being deprecated (because the diagnostic is not
// enabled), warn now that it is deprecated and changes behavior.
bool AddNote = false;
if (PossiblePrototype) {
if (Diags.isIgnored(diag::warn_strict_prototypes,
PossiblePrototype->getLocation())) {
PartialDiagnostic PD =
PDiag(diag::warn_non_prototype_changes_behavior);
if (TypeSourceInfo *TSI = PossiblePrototype->getTypeSourceInfo()) {
if (auto FTL = TSI->getTypeLoc().getAs<FunctionNoProtoTypeLoc>())
PD << FixItHint::CreateInsertion(FTL.getRParenLoc(), "void");
}
Diag(PossiblePrototype->getLocation(), PD);
} else {
AddNote = true;
}
}
// This K&R C function definition definitely changes behavior in C2x,
// so diagnose it.
Diag(FD->getLocation(), diag::warn_non_prototype_changes_behavior)
<< /*definition*/ 1 << /* not supported in C2x */ 0;
// Because this function definition has no prototype and it has
// parameters, it will definitely change behavior in C2x.
Diag(FD->getLocation(), diag::warn_non_prototype_changes_behavior);
if (AddNote)
// If we have a possible prototype for the function which is a user-
// visible declaration, we already tested that it has no prototype.
// This will change behavior in C2x. This gets a warning rather than a
// note because it's the same behavior-changing problem as with the
// definition.
if (PossiblePrototype)
Diag(PossiblePrototype->getLocation(),
diag::note_func_decl_changes_behavior);
diag::warn_non_prototype_changes_behavior)
<< /*declaration*/ 0 << /* conflicting */ 1 << /*subsequent*/ 1
<< /*definition*/ 1;
}
// Warn on CPUDispatch with an actual body.

6
clang/test/C/drs/dr0xx.c
View File

@ -231,13 +231,13 @@ int dr032 = (1, 2); /* expected-warning {{left operand of comma operator has no
/* WG14 DR035: partial
* Questions about definition of functions without a prototype
*/
void dr035_1(a, b) /* expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}} */
void dr035_1(a, b) /* expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}} */
int a(enum b {x, y}); /* expected-warning {{declaration of 'enum b' will not be visible outside of this function}} */
int b; {
int test = x; /* expected-error {{use of undeclared identifier 'x'}} */
}
void dr035_2(c) /* expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}} */
void dr035_2(c) /* expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}} */
enum m{q, r} c; { /* expected-warning {{declaration of 'enum m' will not be visible outside of this function}} */
/* FIXME: This should be accepted because the scope of m, q, and r ends at
* the closing brace of the function per C89 6.1.2.1.
@ -391,7 +391,7 @@ void dr068(void) {
* a prototype causes implicit conversions rather than relying on default
* argument promotion and warm thoughts.
*/
void dr070_1(c) /* expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}} */
void dr070_1(c) /* expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}} */
int c; {
}

2
clang/test/CodeGen/2009-06-01-addrofknr.c
View File

@ -5,7 +5,7 @@ struct funcptr {
int (*func)();
};
static int func(f) // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
static int func(f) // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
void *f;
{
return 0;

10
clang/test/Parser/declarators.c
View File

@ -27,12 +27,12 @@ void test2(int *P, int A) {
}
typedef int atype;
void test3(x, /* expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}} */
void test3(x, /* expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}} */
atype /* expected-error {{unexpected type name 'atype': expected identifier}} */
) int x, atype; {}
void test4(x, x) int x; {} // expected-error {{redefinition of parameter 'x'}} \
// expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
// expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
// PR3031
@ -103,11 +103,11 @@ void *test14b = (void*)test14a; // Make sure test14a didn't get skipped.
long struct X { int x; } test15(void); // expected-error {{'long struct' is invalid}}
void test16(i) int i j; { } // expected-error {{expected ';' at end of declaration}} \
// expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
// expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
void test17(i, j) int i, j k; { } // expected-error {{expected ';' at end of declaration}} \
// expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
// expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
void knrNoSemi(i) int i { } // expected-error {{expected ';' at end of declaration}} \
// expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
// expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
// PR12595
void test18(void) {

2
clang/test/Sema/arg-duplicate.c
View File

@ -1,6 +1,6 @@
// RUN: %clang_cc1 -fsyntax-only -verify %s -std=c99
int f3(y, x, // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
int f3(y, x, // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
x) // expected-error {{redefinition of parameter}}
int y,
x, // expected-note {{previous declaration is here}}

10
clang/test/Sema/knr-def-call.c
View File

@ -1,19 +1,19 @@
// RUN: %clang_cc1 -triple i386-pc-unknown -Wconversion -Wliteral-conversion -fsyntax-only -verify %s
// C DR #316, PR 3626.
void f0(a, b, c, d) int a,b,c,d; {} // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void f0(a, b, c, d) int a,b,c,d; {} // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
void t0(void) {
f0(1); // expected-warning{{too few arguments}}
}
void f1(a, b) int a, b; {} // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void f1(a, b) int a, b; {} // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
void t1(void) {
f1(1, 2, 3); // expected-warning{{too many arguments}}
}
void f2(float); // expected-note{{previous declaration is here}}
void f2(x) float x; { } // expected-warning{{promoted type 'double' of K&R function parameter is not compatible with the parameter type 'float' declared in a previous prototype}} \
expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
typedef void (*f3)(void);
f3 t3(int b) { return b? f0 : f1; } // okay
@ -33,7 +33,7 @@ char *rindex(s, c)
// PR8314
void proto(int);
void proto(x) // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void proto(x) // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
int x;
{
}
@ -45,6 +45,6 @@ void use_proto() {
// PR31020
void func(short d) __attribute__((cdecl)); // expected-note{{previous declaration is here}}
void __attribute__((cdecl)) func(d) // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void __attribute__((cdecl)) func(d) // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
short d; // expected-warning{{promoted type 'int' of K&R function parameter is not compatible with the parameter type 'short' declared in a previous prototype}}
{}

4
clang/test/Sema/knr-variadic-def.c
View File

@ -5,7 +5,7 @@
char *foo = "test";
int test(char*,...);
int test(fmt) // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
int test(fmt) // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
char*fmt;
{
va_list ap;
@ -21,7 +21,7 @@ int test(fmt) // expected-warning {{a function declaration without a prototype i
void exit(); // expected-warning {{a function declaration without a prototype is deprecated in all versions of C}}
int main(argc,argv) // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
int main(argc,argv) // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
int argc;char**argv;
{
exit(test("",foo));

38
clang/test/Sema/warn-deprecated-non-prototype.c
View File

@ -23,15 +23,14 @@ void whatever(void) {
void again() {} // strict-warning {{a function declaration without a prototype is deprecated in all versions of C}}
// On by default warnings
void func(); // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}} \
strict-warning {{a function declaration without a prototype is deprecated in all versions of C}} \
strict-note {{a function declaration without a prototype is not supported in C2x}}
void func(a, b) int a, b; {} // both-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void func(); // both-warning {{a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a subsequent definition}} \
strict-warning {{a function declaration without a prototype is deprecated in all versions of C}}
void func(a, b) int a, b; {} // both-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
void one_more(a, b) int a, b; {} // both-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void one_more(a, b) int a, b; {} // both-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
void sheesh(int a);
void sheesh(a) int a; {} // both-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void sheesh(a) int a; {} // both-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
void another(); // strict-warning {{a function declaration without a prototype is deprecated in all versions of C}}
@ -39,35 +38,26 @@ int main(void) {
another(1, 2); // both-warning {{passing arguments to 'another' without a prototype is deprecated in all versions of C and is not supported in C2x}}
}
void order1(); // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}} \
strict-warning {{a function declaration without a prototype is deprecated in all versions of C}} \
strict-note {{a function declaration without a prototype is not supported in C2x}}
void order1(int i); // both-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void order1(); // both-warning {{a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a subsequent declaration}} \
strict-warning {{a function declaration without a prototype is deprecated in all versions of C}}
void order1(int i); // both-note {{conflicting prototype is here}}
void order2(int i);
void order2(); // both-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}} \
void order2(int i); // both-note {{conflicting prototype is here}}
void order2(); // both-warning {{a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a previous declaration}} \
strict-warning {{a function declaration without a prototype is deprecated in all versions of C}}
void order3(); // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}} \
strict-warning {{a function declaration without a prototype is deprecated in all versions of C}} \
strict-note {{a function declaration without a prototype is not supported in C2x}}
void order3(int i) {} // both-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void order3(); // both-warning {{a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a subsequent definition}} \
strict-warning {{a function declaration without a prototype is deprecated in all versions of C}}
void order3(int i) {} // both-note {{conflicting prototype is here}}
// Just because the prototype is variadic doesn't mean we shouldn't warn on the
// K&R C function definition; this still changes behavior in C2x.
void test(char*,...);
void test(fmt) // both-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void test(fmt) // both-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
char*fmt;
{
}
// FIXME: we get two diagnostics here when running in pedantic mode. The first
// comes when forming the function type for the definition, and the second
// comes from merging the function declarations together. The second is the
// point at which we know the behavior has changed (because we can see the
// previous declaration at that point), but we've already issued the type
// error by that point. It's not ideal to be this chatty, but this situation
// should be pretty rare.
void blapp(int); // both-note {{previous declaration is here}}
void blapp() { } // both-error {{conflicting types for 'blapp'}} \
// strict-warning {{a function declaration without a prototype is deprecated in all versions of C}}

10
clang/test/Sema/warn-strict-prototypes.c
View File

@ -48,7 +48,7 @@ void bar3(void) {
}
// K&R function definition not preceded by full prototype
int foo9(a, b) // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
int foo9(a, b) // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
int a, b;
{
return a + b;
@ -56,17 +56,17 @@ int foo9(a, b) // expected-warning {{a function declaration without a prototype
// Function declaration with no types
void foo10(); // expected-warning {{a function declaration without a prototype is deprecated in all versions of C}} \
expected-note {{a function declaration without a prototype is not supported in C2x}}
expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a subsequent definition}}
// CHECK: fix-it:"{{.*}}":{[[@LINE-2]]:12-[[@LINE-2]]:12}:"void"
// K&R function definition with incomplete param list declared
void foo10(p, p2) void *p; {} // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}} \
void foo10(p, p2) void *p; {} // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}} \
expected-warning {{parameter 'p2' was not declared, defaults to 'int'; ISO C99 and later do not support implicit int}}
void foo11(int p, int p2);
void foo11(p, p2) int p; int p2; {} // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void foo11(p, p2) int p; int p2; {} // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
// PR31020
void __attribute__((cdecl)) foo12(d) // expected-warning {{a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x}}
void __attribute__((cdecl)) foo12(d) // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C2x}}
short d;
{}