Aaron Ballman 7d644e1215 [C11/C2x] Change the behavior of the implicit function declaration warning
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
2022-04-20 11:30:12 -04:00

290 lines
6.1 KiB
C

// RUN: %clang_cc1 -triple x86_64-windows -fborland-extensions -DBORLAND -fsyntax-only -verify -fblocks %s
// RUN: %clang_cc1 -triple x86_64-windows -fms-extensions -fsyntax-only -verify -fblocks %s
#define JOIN2(x,y) x ## y
#define JOIN(x,y) JOIN2(x,y)
#define TEST2(name) JOIN(name,__LINE__)
#define TEST TEST2(test)
typedef int DWORD;
#pragma sysheader begin
struct EXCEPTION_INFO{};
unsigned long __exception_code(void);
#ifdef BORLAND
struct EXCEPTION_INFO* __exception_info(void);
#endif
int __abnormal_termination(void);
#define GetExceptionCode __exception_code
#define GetExceptionInformation __exception_info
#define AbnormalTermination __abnormal_termination
#pragma sysheader end
DWORD FilterExpression(int); // expected-note{{declared here}}
DWORD FilterExceptionInformation(struct EXCEPTION_INFO*);
const char * NotFilterExpression(void);
void TEST(void) {
__try {
__try {
__try {
}
__finally{
}
}
__finally{
}
}
__finally{
}
}
void TEST(void) {
__try {
}
} // expected-error{{expected '__except' or '__finally' block}}
void TEST(void) {
__except (FilterExpression()) { // expected-error{{call to undeclared function '__except'; ISO C99 and later do not support implicit function declarations}} \
// expected-error{{too few arguments to function call, expected 1, have 0}} \
// expected-error{{expected ';' after expression}}
}
}
void TEST(void) {
__finally { } // expected-error{{}}
}
void TEST(void) {
__try{
int try_scope = 0;
} // TODO: expected expression is an extra error
__except( try_scope ? 1 : -1 ) // expected-error{{undeclared identifier 'try_scope'}} expected-error{{expected expression}}
{}
}
void TEST(void) {
__try {
}
// TODO: Why are there two errors?
__except( ) { // expected-error{{expected expression}} expected-error{{expected expression}}
}
}
void TEST(void) {
__try {
}
__except ( FilterExpression(GetExceptionCode()) ) {
}
__try {
}
__except( FilterExpression(__exception_code()) ) {
}
__try {
}
__except( FilterExceptionInformation(__exception_info()) ) {
}
__try {
}
__except(FilterExceptionInformation( GetExceptionInformation() ) ) {
}
}
void TEST(void) {
__try {
}
__except ( NotFilterExpression() ) { // expected-error{{filter expression has non-integral type 'const char *'}}
}
}
void TEST(void) {
int function_scope = 0;
__try {
int try_scope = 0;
}
__except ( FilterExpression(GetExceptionCode()) ) {
(void)function_scope;
(void)try_scope; // expected-error{{undeclared identifier}}
}
}
void TEST(void) {
int function_scope = 0;
__try {
int try_scope = 0;
}
__finally {
(void)function_scope;
(void)try_scope; // expected-error{{undeclared identifier}}
}
}
void TEST(void) {
int function_scope = 0;
__try {
}
__except( function_scope ? 1 : -1 ) {}
}
#ifdef BORLAND
void TEST(void) {
(void)__abnormal_termination(); // expected-error{{only allowed in __finally block}}
(void)AbnormalTermination(); // expected-error{{only allowed in __finally block}}
__try {
(void)AbnormalTermination; // expected-error{{only allowed in __finally block}}
(void)__abnormal_termination; // expected-error{{only allowed in __finally block}}
}
__except( 1 ) {
(void)AbnormalTermination; // expected-error{{only allowed in __finally block}}
(void)__abnormal_termination; // expected-error{{only allowed in __finally block}}
}
__try {
}
__finally {
AbnormalTermination();
__abnormal_termination();
}
}
#endif
void TEST(void) {
(void)__exception_info(); // expected-error{{only allowed in __except filter expression}}
(void)GetExceptionInformation(); // expected-error{{only allowed in __except filter expression}}
}
void TEST(void) {
#ifndef BORLAND
(void)__exception_code; // expected-error{{builtin functions must be directly called}}
#endif
(void)__exception_code(); // expected-error{{only allowed in __except block or filter expression}}
(void)GetExceptionCode(); // expected-error{{only allowed in __except block or filter expression}}
}
void TEST(void) {
__try {
} __except(1) {
GetExceptionCode(); // valid
GetExceptionInformation(); // expected-error{{only allowed in __except filter expression}}
}
}
void test_seh_leave_stmt(void) {
__leave; // expected-error{{'__leave' statement not in __try block}}
__try {
__leave;
__leave 4; // expected-error{{expected ';' after __leave statement}}
} __except(1) {
__leave; // expected-error{{'__leave' statement not in __try block}}
}
__try {
__leave;
} __finally {
__leave; // expected-error{{'__leave' statement not in __try block}}
}
__leave; // expected-error{{'__leave' statement not in __try block}}
}
void test_jump_out_of___finally(void) {
while(1) {
__try {
} __finally {
continue; // expected-warning{{jump out of __finally block has undefined behavior}}
}
}
__try {
} __finally {
while (1) {
continue;
}
}
// Check that a deep __finally containing a block with a shallow continue
// doesn't trigger the warning.
while(1) {{{{
__try {
} __finally {
^{
while(1)
continue;
}();
}
}}}}
while(1) {
__try {
} __finally {
break; // expected-warning{{jump out of __finally block has undefined behavior}}
}
}
switch(1) {
case 1:
__try {
} __finally {
break; // expected-warning{{jump out of __finally block has undefined behavior}}
}
}
__try {
} __finally {
while (1) {
break;
}
}
__try {
__try {
} __finally {
__leave; // expected-warning{{jump out of __finally block has undefined behavior}}
}
} __finally {
}
__try {
} __finally {
__try {
__leave;
} __finally {
}
}
__try {
} __finally {
return; // expected-warning{{jump out of __finally block has undefined behavior}}
}
__try {
} __finally {
^{
return;
}();
}
}
void test_typo_in_except(void) {
__try {
} __except(undeclared_identifier) { // expected-error {{use of undeclared identifier 'undeclared_identifier'}} expected-error {{expected expression}}
}
}