1.3 Unsupported GCC features

The following GCC options are not currently supported on Palm OS:

-p

-pg

-a

-ax

-fprofile-arcs

-fbranch-probabilities

Probably profiling is unsupported. Certainly the support functions in `libgcc' aren't being included, because they depend on non-existent stdio support.

-ftest-coverage

A similar comment applies to the gcov data file.

-ffunction-sections

This option sets each function's section after function calls are generated. This is too late to be effective because we need to emit special code for cross-section function calls.

-mbitfield

-m68020

-m68881

These and other M68K hardware selection options will cause your programs to fail horribly.

-mrtd

This selects code generation patterns which disagree with the conventions used by the Palm OS API functions, so will fail horribly.

There are also the following caveats:

• While describing the section attribute, the GCC manual suggests using the linker to split an executable into sections. Just like `-ffunction-sections', this doesn't work.
• The __complex__ extension doesn't work.
• The `-Wmultichar' warning is off by default, even if you use `-Wall'.
• If `-mpcrel' is on, as it always is, any `-fpic' or `-fPIC' options are ineffective: `-mpcrel' always implies `-fpic'.
• Because we care about code size (and don't have an instruction cache), too much of the following is probably counter-productive: `-ffunction-cse', `-funroll-loops', `-funroll-all-loops'. Hence these options are not implied by the `-O' flags, but must be selected explicitly.
• If you use 64K code resources, the linker `-r' option will not always work. Fortunately, these are both unnecessary.
• Changing the specs file with `-specs=file' or invoking m68k-palmos-as or m68k-palmos-ld directly should be done with caution: proper operation is quite dependent on options set in the default specs file.

This document was generated by root on October, 25 2005 using texi2html 1.76.