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C Pitfalls
C is a powerful language that offers almost absolute control and maximum performance which necessarily comes with responsibility and danger of shooting yourself in the foot. Without knowledge of the pitfalls you may well find yourself fallen into one of them.
Unless specified otherwise, this article supposes the C99 standard of the C language.
Undefined Behavior
Undefined behavior is any behavior that is not described in the specification of the language; this is mostly done on purpose as to allow some implementation freedom which allows implementing the language in a way that is most efficient on given platform. Undefined behavior may be completely random (unpredictable) or implementation-specified (consistent within each implementation but potentially different for each of them). In any case, it is highly advised to avoid any undefined behavior in absolute majority of cases. Description of some of the undefined behavior cases follow.
Data type sizes including int and char may not be the same on each platform. Even though we almost take it for granted than char is 8 bits wide, in theory it can be wider. The int (and unsigned int) type width should reflect the architectures native integer type, so nowadays mostly it's mostly 32 or 64 bits. To deal with this we can use the standard library limits.h and stdint.h headers.
Char data type signedness is not defined. The signedness can be explicitly "forced" by specifying signed char or unsigned char.
Bit shifts by type width or more are undefined. Also bit shifts by negative values are undefined. So e.g. x >> 8 is undefined if width of the data type of x is 8 bits.
TODO
Memory Unsafety
TODO