The GCC option -iwithprefix does not match the documentation.
Is there any reason for this discrepancy?
The GCC option -iwithprefix is documented in gcc/doc/cppopts.texi
@item -iwithprefix @var{dir}
@itemx -iwithprefixbefore @var{dir}
@opindex iwithprefix
@opindex iwithprefixbefore
Append @var{dir} to the prefix specified previously with
@option{-iprefix}, and add the resulting directory to the include search
path. @option{-iwithprefixbefore} puts it in the same place @option{-I}
would; @option{-iwithprefix} puts it where @option{-idirafter} would.
However, -iwithprefix does not put the search path where -idirafter
would, instead it puts the search path at the top of the SYSTEM chain.
See gcc/c-opts.c:
...
case OPT_idirafter:
add_path (xstrdup (arg), AFTER, 0, true);
break;
...
case OPT_iwithprefix:
add_prefixed_path (arg, SYSTEM);
break;
The order of the compilers SYSTEM paths is important to the correct
processing of C++ header #include_next macros.
If you use -iwithprefix to modify the compilers -iprefix path to define
a header that matches a SYSTEM header, the compiler removes the
redundant SYSTEM path definition and leaves the one generated by
-iwithprefix (it's the same path just in a different search order).
However, since -iwithprefix moved the header definition to the *top* of
the search list, when #include_next is used, it may result in a missing
header.
If -iwithprefix implemented what was documented, then it appears that
there would be no issue.
Cheers,
Carlos.
--
Carlos O'Donell
CodeSourcery
[EMAIL PROTECTED]
(650) 331-3385 x716
