ISO C features missing from microlib
2.4 ISO C features missing from microlib
Microlib does not support all ISO C90 features.
Major ISO C90 features not supported by microlib are:
- Wide character and multibyte
- 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,
All functions defined in Normative Addendum 1 are not supported by microlib.
- Operating system interaction
- Almost all functions that interact with an operating system are not supported by
microlib. For example,
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_init(), which it needs), if required.
- File I/O
By default, all the
that interact with a file pointer return an error if called. The only exceptions to
this are the three standard streams
You can change this behavior using
#pragma import(__use_full_stdio). Use of this
pragma provides a microlib version of
supports ANSI C, with only the following exceptions:
- The error and
EOF indicators are
not supported, so
- All streams are unbuffered, so
- Configurable locale
- The default C locale is the only one available.
- The functions
raise() are provided but microlib does not generate signals.
The only exception to this is if the program explicitly calls
- Floating-point support
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:
- Operations involving NaNs, infinities or input denormals produce indeterminate
results. Operations that produce a result that is nonzero but very small in value,
- IEEE exceptions cannot be flagged by microlib, and there is no
fp_status() register in microlib.
- The sign of zero is not treated as significant by microlib, and zeroes that are
output from microlib floating-point arithmetic have an unknown sign bit.
- Only the default rounding mode is supported.
- Position independent and thread
- 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.
- Command-line arguments
argv parameters are
undefined and cannot be used to access command-line arguments.