aaronpuchert created this revision.
aaronpuchert added reviewers: arphaman, bruno, rsmith.
Herald added subscribers: cfe-commits, dexonsmith.
Herald added a project: clang.
Zero-parameter K&R definitions specify that the function has no
parameters, but they are still not prototypes, so calling the function
with the wrong number of parameters is just a warning, not an error.
The C11 standard doesn't seem to directly define what a prototype is,
but it can be inferred from 6.9.1p7: "If the declarator includes a
parameter type list, the list also specifies the types of all the
parameters; such a declarator also serves as a function prototype
for later calls to the same function in the same translation unit."
This refers to 6.7.6.3p5: "If, in the declaration “T D1
<https://reviews.llvm.org/D1>”, D1 <https://reviews.llvm.org/D1> has
the form
D(parameter-type-list)
or
D(identifier-list_opt)
[...]". Later in 6.11.7 it also refers only to the parameter-type-list
variant as prototype: "The use of function definitions with separate
parameter identifier and declaration lists (not prototype-format
parameter type and identifier declarators) is an obsolescent feature."
We already correctly treat an empty parameter list as non-prototype
declaration, so we can just take that information.
GCC also warns about this with -Wstrict-prototypes.
This shouldn't affect C++, because there all FunctionType's are
FunctionProtoTypes. I added a simple test for that.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D66919
Files:
clang/lib/Sema/SemaDecl.cpp
clang/test/Sema/warn-strict-prototypes.c
clang/test/Sema/warn-strict-prototypes.cpp
clang/test/Sema/warn-strict-prototypes.m
Index: clang/test/Sema/warn-strict-prototypes.m
===================================================================
--- clang/test/Sema/warn-strict-prototypes.m
+++ clang/test/Sema/warn-strict-prototypes.m
@@ -10,7 +10,7 @@
@end
-void foo() {
+void foo() { // expected-warning {{this old-style function definition is not
preceded by a prototype}}
void (^block)() = // expected-warning {{this block declaration is not a
prototype}}
^void(int arg) { // no warning
};
Index: clang/test/Sema/warn-strict-prototypes.cpp
===================================================================
--- /dev/null
+++ clang/test/Sema/warn-strict-prototypes.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -verify -fsyntax-only -Wstrict-prototypes %s
+// expected-no-diagnostics
+
+void decl();
+void decl_void(void);
+
+void def() {}
+void def_void(void) {}
Index: clang/test/Sema/warn-strict-prototypes.c
===================================================================
--- clang/test/Sema/warn-strict-prototypes.c
+++ clang/test/Sema/warn-strict-prototypes.c
@@ -7,9 +7,9 @@
// 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() {}
+// function definition with 0 params, no prototype.
+void foo1() {} // expected-warning {{this old-style function definition is not
preceded by a prototype}}
+// function definition with 0 params, prototype.
void foo2(void) {}
// function type typedef unspecified params
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -13395,11 +13395,7 @@
// Warn if K&R function is defined without a previous declaration.
// This warning is issued only if the definition 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) {
+ if (!FD->hasWrittenPrototype()) {
TypeSourceInfo *TI = FD->getTypeSourceInfo();
TypeLoc TL = TI->getTypeLoc();
FunctionTypeLoc FTL = TL.getAsAdjusted<FunctionTypeLoc>();
Index: clang/test/Sema/warn-strict-prototypes.m
===================================================================
--- clang/test/Sema/warn-strict-prototypes.m
+++ clang/test/Sema/warn-strict-prototypes.m
@@ -10,7 +10,7 @@
@end
-void foo() {
+void foo() { // expected-warning {{this old-style function definition is not preceded by a prototype}}
void (^block)() = // expected-warning {{this block declaration is not a prototype}}
^void(int arg) { // no warning
};
Index: clang/test/Sema/warn-strict-prototypes.cpp
===================================================================
--- /dev/null
+++ clang/test/Sema/warn-strict-prototypes.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -verify -fsyntax-only -Wstrict-prototypes %s
+// expected-no-diagnostics
+
+void decl();
+void decl_void(void);
+
+void def() {}
+void def_void(void) {}
Index: clang/test/Sema/warn-strict-prototypes.c
===================================================================
--- clang/test/Sema/warn-strict-prototypes.c
+++ clang/test/Sema/warn-strict-prototypes.c
@@ -7,9 +7,9 @@
// 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() {}
+// function definition with 0 params, no prototype.
+void foo1() {} // expected-warning {{this old-style function definition is not preceded by a prototype}}
+// function definition with 0 params, prototype.
void foo2(void) {}
// function type typedef unspecified params
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -13395,11 +13395,7 @@
// Warn if K&R function is defined without a previous declaration.
// This warning is issued only if the definition 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) {
+ if (!FD->hasWrittenPrototype()) {
TypeSourceInfo *TI = FD->getTypeSourceInfo();
TypeLoc TL = TI->getTypeLoc();
FunctionTypeLoc FTL = TL.getAsAdjusted<FunctionTypeLoc>();
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