File: libtool.info,  Node: Compile mode,  Next: Link mode,  Up: Invoking libtool

4.1 Compile mode
================

For “compile” mode, MODE-ARGS is a compiler command to be used in
creating a "standard" object file.  These arguments should begin with
the name of the C compiler, and contain the ‘-c’ compiler flag so that
only an object file is created.

   Libtool determines the name of the output file by removing the
directory component from the source file name, then substituting the
source code suffix (e.g. ‘.c’ for C source code) with the library object
suffix, ‘.lo’.

   If shared libraries are being built, any necessary PIC generation
flags are substituted into the compilation command.

   The following components of MODE-ARGS are treated specially:

‘-o’
     Note that the ‘-o’ option is now fully supported.  It is emulated
     on the platforms that don't support it (by locking and moving the
     objects), so it is really easy to use libtool, just with minor
     modifications to your Makefiles.  Typing for example
          libtool --mode=compile gcc -c foo/x.c -o foo/x.lo
     will do what you expect.

     Note, however, that, if the compiler does not support ‘-c’ and
     ‘-o’, it is impossible to compile ‘foo/x.c’ without overwriting an
     existing ‘./x.o’.  Therefore, if you do have a source file ‘./x.c’,
     make sure you introduce dependencies in your ‘Makefile’ to make
     sure ‘./x.o’ (or ‘./x.lo’) is re-created after any sub-directory's
     ‘x.lo’:

          x.o x.lo: foo/x.lo bar/x.lo

     This will also ensure that make won't try to use a temporarily
     corrupted ‘x.o’ to create a program or library.  It may cause
     needless recompilation on platforms that support ‘-c’ and ‘-o’
     together, but it's the only way to make it safe for those that
     don't.

‘-no-suppress’
     If both PIC and non-PIC objects are being built, libtool will
     normally suppress the compiler output for the PIC object
     compilation to save showing very similar, if not identical
     duplicate output for each object.  If the ‘-no-suppress’ option is
     given in compile mode, libtool will show the compiler output for
     both objects.

‘-prefer-pic’
     Libtool will try to build only PIC objects.

‘-prefer-non-pic’
     Libtool will try to build only non-PIC objects.

‘-shared’
     Even if Libtool was configured with ‘--enable-static’, the object
     file Libtool builds will not be suitable for static linking.
     Libtool will signal an error if it was configured with
     ‘--disable-shared’, or if the host does not support shared
     libraries.

‘-static’
     Even if libtool was configured with ‘--disable-static’, the object
     file Libtool builds *will* be suitable for static linking.

‘-Wc,FLAG’
‘-Xcompiler FLAG’
     Pass a flag directly to the compiler.  With ‘-Wc,’, multiple flags
     may be separated by commas, whereas ‘-Xcompiler ’ passes through
     commas unchanged.