Exotic architectures the standards committees care about

Question

I know that the C and C++ standards leave many aspects of the language implementation-defined just because if there is an architecture with other characteristics, it would b

Answer 1

CHAR_BITS

According to gcc source code:

CHAR_BIT is 16 bits for 1750a, dsp16xx architectures.
CHAR_BIT is 24 bits for dsp56k architecture.
CHAR_BIT is 32 bits for c4x architecture.

You can easily find more by doing:

find $GCC_SOURCE_TREE -type f | xargs grep "#define CHAR_TYPE_SIZE"

or

find $GCC_SOURCE_TREE -type f | xargs grep "#define BITS_PER_UNIT"

if CHAR_TYPE_SIZE is appropriately defined.

IEEE 754 compliance

If target architecture doesn't support floating point instructions, gcc may generate software fallback witch is not the standard compliant by default. More than, special options (like -funsafe-math-optimizations witch also disables sign preserving for zeros) can be used.