Hi, we recently encountered a build failure of Octave on alpha [1,2] due to an added indirect dependency on the fpieee gnulib module, which appends compiler options to CPPFLAGS that don't necessarily belong there.
This module apparently adds either "-mieee" or "-ieee" to CPPFLAGS when building on certain systems. These are decidedly not preprocessor flags, but are likely added this way as a shortcut to ensure that they are used when compiling any language. However, the working assumption that what works for $(CC) will work for anything that takes CPPFLAGS is not necessarily true. For example, even invoking $(CPP) $(CPPFLAGS) using gcc would fail with an error in this environment. In the case of Octave, it fails because CPPFLAGS are passed on to other tools (such as Qt moc) that will work with standard preprocessor options like -D and -I, but not -mieee. Our workaround is to simply filter these options out of CPPFLAGS, because Octave has already had its own logic to append the appropriate compiler options to CFLAGS and CXXFLAGS for several years. I'm not sure what an appropriate fix for this would be in the general case, but ideally it would avoid adding these options to project-wide CPPFLAGS where they really don't belong. If it were possible to add the -mieee or -ieee option to language-specific FLAGS variables used by a given project, that would be a better solution. Less ideally, it could stuff the option into an IEEE_CFLAGS variable, which a project would then have to know about and explicitly use or add to its own CFLAGS/CXXFLAGS/etc, potentially breaking existing uses. [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=746924 [2] http://savannah.gnu.org/bugs/?42839 Thoughts? Thanks, -- mike
