On 03/02/19 05:08, J. Gareth Moreton wrote:
Basically, if you declare a public symbol (either using the "public" directive or putting it in the interface section of a unit) with a name that's identical to an internal symbol (I used "FPC_ABSMASK_DOUBLE"), you get a 'duplicate symbol' linker error... in fact, Lazarus doesn't even display the error (see bug #34996) - it only appears if you run the compiler from the command line.
The FPC (and _FPC) namespace is reserved for internal use. Detecting such clashes is not possible without adding all declared external symbols to hash tables, which would reduce both compilation speed and increase memory usage. I think it's better to simply document that such symbols are reserved for compiler and RTL usage.
You can get around the above issue if you simply rename the constant or keep it private. However, there is one other issue that is not so easy to circumvent, and that's when you try to call an internal function through assembly language (in this instance, I'm assuming the code is not cross-platform and I'll be calling the x86_64 version of fpc_int_real, which is "nostackframe" and only modifies XMM0 and RAX):
Calling internal functions directly is unsupported, which is the reason why they are made inaccessible from regular code. Their signature or behaviour can change across compiler versions (or they may even disappear altogether). You can hack around it by declaring external functions mapping to the symbol name of the internal function, but again, that is completely unsupported.
Jonas _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
