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Diffstat (limited to 'newlib/README')
| -rw-r--r-- | newlib/README | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/newlib/README b/newlib/README index adad87111..a3d915dda 100644 --- a/newlib/README +++ b/newlib/README @@ -372,6 +372,73 @@ One feature can be enabled by specifying `--enable-FEATURE=yes' or invoke clean-up functions such as _fini or global destructors. Disabled by default. +`--enable-newlib-nano-formatted-io' + This builds NEWLIB with a special implementation of formatted I/O + functions, designed to lower the size of application on small systems + with size constraint issues. This option does not affect wide-char + formatted I/O functions. Some notes about the feature: + 1) The non-wide-char formatted I/O functions only support the C89 + standard. The only exception is the configuration option provides + limited support for long double. Internally, the nano formatted I/O + functions use double so accuracy is only guaranteed to double + precision. + 2) Floating-point support is split out of the formatted I/O code into + weak functions which are not linked by default. Programs that need + floating-point I/O support must explicitly request linking of one or + both of the floating-point functions: _printf_float or _scanf_float. + This can be done at link time using the -u option which can be passed + to either gcc or ld. The -u option forces the link to resolve those + function references. Floating-point format specifiers are recognized + by default, but if the floating-point functions are not explicitly + linked in, this may result in undefined behavior for programs that + need floating-point I/O support. + 3) Integer-only versions of the formatted I/O functions (the iprintf/ + iscanf family) simply alias their regular counter-parts. + The affected functions are: + + diprintf vdiprintf + + siprintf fiprintf iprintf sniprintf asiprintf asniprintf + + siscanf fiscanf iscanf + + viprintf vfiprintf vsiprintf vsniprintf vasiprintf vasniprintf + + viscanf vfiscanf vsiscanf + + _diprintf_r _vdiprintf_r + + _siprintf_r _fiprintf_r _iprintf_r _sniprintf_r _asiprintf_r + _asniprintf_r + + _siscanf_r _fiscanf_r _iscanf_r + + _viprintf_r _vfiprintf_r _vsiprintf_r _asniprintf_r _vasiprintf_r + _vasniprintf_r + + _viscanf_r _vfiscanf_r _vsiscanf_r + + 4) As mentioned, the option does not affect wide-char formatted I/O. + The following configuration options are ignored for non-wide-char + formatted I/O functions, and can be thought of as disabled. + + enable-newlib-io-pos-args + enable-newlib-io-c99-formats + enable-newlib-io-long-long + enable-newlib-io-long-double + enable-newlib-mb + + Additionally, "enable/disable-newlib-io-float" is supported in + this specific implementation, one can use "disable-newlib-io-float" + to further reduce code size. In this case, the floating-point + specifiers will not be recognized or handled, and the -u option + will not work either. + + 5) As a rule, no features from outside of C89 standard will be + considered in this implementation. + + Disabled by default. + Running the Testsuite ===================== |