ISO C features missing from microlib

All functions dealing with wide characters or multibyte strings are not supported by microlib. A link error is generated if these are used. For example, mbtowc(), wctomb(), mbstowcs() and wcstombs(). All functions defined in Normative Addendum 1 are not supported by microlib.

Almost all functions that interact with an operating system are not supported by microlib. For example, abort(), exit(), atexit(), assert(), time(), system() and getenv(). An exception is clock(). A minimal implementation of clock() has been provided, which returns only -1, not the elapsed time. You may reimplement clock() (and _clock_init(), which it needs), if required.

By default, all the stdio functions that interact with a file pointer return an error if called. The only exceptions to this are the three standard streams stdin, stdout and stderr.

You can change this behavior using #pragma import(__use_full_stdio). Use of this pragma provides a microlib version of stdio that supports ANSI C, with only the following exceptions:

The default C locale is the only one available.

The functions signal() and raise() are provided but microlib does not generate signals. The only exception to this is if the program explicitly calls raise().

Floating-point support diverges from IEEE 754 in the following ways, but uses the same data formats and matches IEEE 754 in operations involving only normalized numbers:

Microlib has no reentrant variant. Microlib does not provide mutex locks to guard against code that is not thread safe. Use of microlib is not compatible with FPIC or RWPI compilation modes, and although ROPI code can be linked with microlib, the resulting binary is not ROPI-compliant overall.