Re: Flags that need special handling.

[Ralf Wildenhues]

Hello Ake,

thanks for the report.

* Ake Sandgren wrote on Thu, Mar 18, 2010 at 03:55:11PM CET:
> When using the PathScale compiler and certain flags that are needed both
> at compile and link time libtool is stripping them out from the link
> command.

First off, a general remark.  libtool only strips unknown flags when
creating libraries (not when compiling only, or when creating programs).
This is done because some flags are harmful to pass on *without* also
changing some other libtool semantics.  So when we allow to let through
some flags unconditionally, we need to be sure that libtool does not
interfere with the flags.

That being said, you should never need to wait for libtool to fix this
handling: you can get libtool to pass through flags by prepending them
with one of '-Wc,', '-Wl,', '-Xcompiler ', or '-Xlinker '.  The first
one is for flags that the compiler driver should get, the second for
flags for the linker, and the last two are only needed if the args
contain commas that should not be converted.

Since libtool is mostly not used during configure scripts, you may need
to override LDFLAGS at 'make' time for this to work.  (The libtool flags
also work when creating programs, or in compile mode, at least in the
current git libtool; ugh.)

> The flags found so far are; -ipa, -Ofast and -IPA*

I haven't checked the PathScale manual yet, but -ipa and -IPA* sound
like they have to do with inter-procedural analysis.  IIRC then some
compilers may generate additional objects for this, but I'm not sure
whether that works seamlessly when creating both static and shared
libraries.

What does -Ofast do?

Thanks,
Ralf