7d644e1215
C89 had a questionable feature where the compiler would implicitly declare a function that the user called but was never previously declared. The resulting function would be globally declared as extern int func(); -- a function without a prototype which accepts zero or more arguments. C99 removed support for this questionable feature due to severe security concerns. However, there was no deprecation period; C89 had the feature, C99 didn't. So Clang (and GCC) both supported the functionality as an extension in C99 and later modes. C2x no longer supports that function signature as it now requires all functions to have a prototype, and given the known security issues with the feature, continuing to support it as an extension is not tenable. This patch changes the diagnostic behavior for the -Wimplicit-function-declaration warning group depending on the language mode in effect. We continue to warn by default in C89 mode (due to the feature being dangerous to use). However, because this feature will not be supported in C2x mode, we've diagnosed it as being invalid for so long, the security concerns with the feature, and the trivial workaround for users (declare the function), we now default the extension warning to an error in C99-C17 mode. This still gives users an easy workaround if they are extensively using the extension in those modes (they can disable the warning or use -Wno-error to downgrade the error), but the new diagnostic makes it more clear that this feature is not supported and should be avoided. In C2x mode, we no longer allow an implicit function to be defined and treat the situation the same as any other lookup failure. Differential Revision: https://reviews.llvm.org/D122983
124 lines
4.3 KiB
C
124 lines
4.3 KiB
C
// RUN: %clang_cc1 -fsyntax-only -verify %s -triple i386-pc-unknown
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// RUN: %clang_cc1 -fsyntax-only -verify %s -triple x86_64-apple-darwin9
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// RUN: %clang_cc1 -fsyntax-only -fms-compatibility -DMS -verify %s -triple x86_64-pc-win32
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void f1(int a)
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{
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__builtin_va_list ap;
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__builtin_va_start(ap, a, a); // expected-error {{too many arguments to function}}
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__builtin_va_start(ap, a); // expected-error {{'va_start' used in function with fixed args}}
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}
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void f2(int a, int b, ...)
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{
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__builtin_va_list ap;
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__builtin_va_start(ap, 10); // expected-warning {{second argument to 'va_start' is not the last named parameter}}
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__builtin_va_start(ap, a); // expected-warning {{second argument to 'va_start' is not the last named parameter}}
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__builtin_va_start(ap, b);
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}
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void f3(float a, ...) { // expected-note 2{{parameter of type 'float' is declared here}}
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__builtin_va_list ap;
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__builtin_va_start(ap, a); // expected-warning {{passing an object that undergoes default argument promotion to 'va_start' has undefined behavior}}
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__builtin_va_start(ap, (a)); // expected-warning {{passing an object that undergoes default argument promotion to 'va_start' has undefined behavior}}
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}
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// stdarg: PR3075 and PR2531
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void f4(const char *msg, ...) {
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__builtin_va_list ap;
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__builtin_stdarg_start((ap), (msg));
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__builtin_va_end (ap);
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}
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void f5(void) {
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__builtin_va_list ap;
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__builtin_va_start(ap,ap); // expected-error {{'va_start' used in function with fixed args}}
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}
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void f6(int a, ...) {
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__builtin_va_list ap;
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__builtin_va_start(ap); // expected-error {{too few arguments to function}}
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}
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// PR3350
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void
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foo(__builtin_va_list authors, ...) {
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__builtin_va_start (authors, authors);
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(void)__builtin_va_arg(authors, int);
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__builtin_va_end (authors);
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}
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void f7(int a, ...) {
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__builtin_va_list ap;
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__builtin_va_start(ap, a);
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// FIXME: This error message is sub-par.
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__builtin_va_arg(ap, int) = 1; // expected-error {{expression is not assignable}}
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int *x = &__builtin_va_arg(ap, int); // expected-error {{cannot take the address of an rvalue}}
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__builtin_va_end(ap);
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}
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void f8(int a, ...) {
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__builtin_va_list ap;
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__builtin_va_start(ap, a);
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(void)__builtin_va_arg(ap, void); // expected-error {{second argument to 'va_arg' is of incomplete type 'void'}}
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__builtin_va_end(ap);
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}
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enum E { x = -1, y = 2, z = 10000 };
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void f9(__builtin_va_list args)
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{
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(void)__builtin_va_arg(args, float); // expected-warning {{second argument to 'va_arg' is of promotable type 'float'}}
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(void)__builtin_va_arg(args, enum E); // Don't warn here in C
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(void)__builtin_va_arg(args, short); // expected-warning {{second argument to 'va_arg' is of promotable type 'short'}}
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(void)__builtin_va_arg(args, char); // expected-warning {{second argument to 'va_arg' is of promotable type 'char'}}
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}
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void f10(int a, ...) {
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int i;
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__builtin_va_list ap;
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i = __builtin_va_start(ap, a); // expected-error {{assigning to 'int' from incompatible type 'void'}}
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__builtin_va_end(ap);
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}
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void f11(short s, ...) { // expected-note {{parameter of type 'short' is declared here}}
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__builtin_va_list ap;
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__builtin_va_start(ap, s); // expected-warning {{passing an object that undergoes default argument promotion to 'va_start' has undefined behavior}}
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__builtin_va_end(ap);
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}
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void f12(register int i, ...) { // expected-note {{parameter of type 'int' is declared here}}
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__builtin_va_list ap;
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__builtin_va_start(ap, i); // expected-warning {{passing a parameter declared with the 'register' keyword to 'va_start' has undefined behavior}}
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__builtin_va_end(ap);
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}
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enum __attribute__((packed)) E1 {
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one1
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};
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void f13(enum E1 e, ...) {
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__builtin_va_list va;
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__builtin_va_start(va, e);
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#ifndef MS
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// In Microsoft compatibility mode, all enum types are int, but in
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// non-ms-compatibility mode, this enumeration type will undergo default
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// argument promotions.
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// expected-note@-7 {{parameter of type 'enum E1' is declared here}}
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// expected-warning@-6 {{passing an object that undergoes default argument promotion to 'va_start' has undefined behavior}}
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#endif
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__builtin_va_end(va);
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}
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void f14(int e, ...) {
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// expected-error@+3 {{call to undeclared library function 'va_start'}}
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// expected-note@+2 {{include the header <stdarg.h>}}
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// expected-error@+1 {{too few arguments to function call}}
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va_start();
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__builtin_va_list va;
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va_start(va, e);
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}
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