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0001775

CMake

public

2005-04-15 14:40

2006-10-04 14:41

Reporter

Brad King

Assigned To

Brad King

Priority

high

Severity

major

Reproducibility

always

Status

closed

Resolution

won't fix

Platform

OS Version

Product Version

Target Version

Fixed in Version

Summary

0001775: CheckFunctionExists and intrinsic functions

Description

The current implementation of CHECK_FUNCTION_EXISTS looks for function foo like this:

char foo();
int main() { foo(); return 0; }

which works in C because there is no mangling so the function can exist with any signature in the standard library. This fails for "intrinsic" functions on Visual Studio optimizing compilers with the /O2 option. Functions like memcmp are builtin and have a signature known to the compiler. Then the call to it fails even though the function exists.

We could instead use this implementation:

char memcmp();
int cmakeRequireSymbol(int n, ...) { return n; }
int main()
{
return cmakeRequireSymbol(0, &memcmp);
}

With this version the real signature of the function does not matter but it still requires the function to exist. By making the return value depend on the code it guarantees that the code requiring the symbol will not be optimized away.

Issue History
Date Modified	Username	Field	Change

Notes
(0005178) Brad King (manager) 2006-10-04 14:41	CHECK_FUNCTION_EXISTS is now deprecated anyway for reasons like this. CHECK_SYMBOL_EXISTS and other variants handle it.

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