Appendix G of the ISO C standard (ISO/IEC 9899:1990 (E)) collates information about portability issues. Sub-clause G3 lists the behavior that each implementation must document. The following topics correspond to the relevant sections of sub-clause G3. They describe aspects of the ARM C compiler and C library, not defined by the ISO C standard, that are implementation-defined.
The support for the wctype.h and wchar.h headers excludes wide file operations.