Compilation Problems

Compilation Problems

C++ has been standardized for decades, or it seems like that. So, I feel like it should be easier to get C++ code to compile. And yet, I find myself sometimes spending an hour or two getting past a few darn compiler errors. Most compilers have a treat-warnings-as-errors mode. Come on, I want the reverse.

Some of the main issues that will have a C++ program compile on one C++ compiler (e.g. MSVS) but not on another (e.g. GCC) include:

• const correctness
• Permissive versus non-permissive modes
• Pointer type casting

const correctness refer to the careful use of “const” to mark not just named constants, but also all unchanging read-only data types. If it's “const” then it cannot be changed; if it's non-const, then it's writable. People have different levels of feelings about whether this is a good idea. There are the fastidious Vogon-relative rule-followers who want it, and the normal reasonable pragmatic people who don't. Can you see which side I'm on?

Anyway, to get non-const-correct code (i.e. mine) to compile on GCC or MSVS, you need to turn off the fussy modes. On MSVS, there's a “permissive” flag in “Conformance Mode” in Project Settings that you have to turn off.

Pointer type casting is another issue. C++ for AI has a lot of problems with pointer types, mainly because C++ standardizers back in the 1990s neglected to create a “short float” 16-bit floating-point type. Theoretically, you're not supposed to cast between different pointer types, like “int*” and “char*”. And theoretically, you're supposed to use “void*” for generic addresses, rather than “char*” or “unsigned char*”. But, you know, this is AI, so them rules is made to be broken, and the C++ standardizer committees finally admitted as much when they created the various special types of casts about 20 years later (i.e., reinterpret_cast).

Anyway, the strategies for getting a non-compiling pointer cast to work include:

• Just casting it to whatever you want.
• Turning on permissive mode
• Casting it to void* and back again (i.e. “x=*(int*)(void*)(char*)&c”)
• Using “reinterpret_cast” like a Goody Two-Shoes.

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