On 01/13/2013 09:01 PM, Nick Bowler wrote: > If subdir-objects is made the default Automake behaviour, packages > will need to add AM_PROG_CC_C_O to their configure.ac. Instead of > that, let's just make the functionality provided by AM_PROG_CC_C_O > mandatory for C projects, and have Automake automatically call it > as required. > > This change should have no effect on packages which explicitly call > AM_PROG_CC_C_O already. > > * m4/init.m4: Have AM_INIT_AUTOMAKE arrange for AM_PROG_CC_C_O to be > called if necessary. > --- > m4/init.m4 | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/m4/init.m4 b/m4/init.m4 > index 7535706..6c48704 100644 > --- a/m4/init.m4 > +++ b/m4/init.m4 > @@ -109,6 +109,11 @@ AC_PROVIDE_IFELSE([AC_PROG_OBJCXX], > [m4_define([AC_PROG_OBJCXX], > > m4_defn([AC_PROG_OBJCXX])[_AM_DEPENDENCIES([OBJCXX])])])dnl > ]) > +dnl Automatically invoke AM_PROG_CC_C_O as necessary. Since AC_PROG_CC is > +dnl usually called after AM_INIT_AUTOMAKE, we arrange for the test to be > +dnl done later by AC_CONFIG_COMMANDS_PRE. > This would also have the advantage that we shouldn't worry about possible $CC rewrites between the AC_PROG_CC and the AC_OUTPUT invocation. Your approach might actually be not only the simplest, but also the sanest one.
That said, I believe we'd still have to fix AM_PROG_CC_C_O not to rely on the broken AC_PROG_CC_C_O semantics of checking *both* '$CC' and 'cc' for "-c -o" support. But that is quite orthogonal to your patch, and material for a follow-up anyway. Another useful follow-up would be to move the AM_PROG_CC_C_O in a private macro (to be expanded in AC_CONFIG_COMMANDS_PRE like you did above), and make AM_PROG_CC_C_O a no-op (without runtime deprecation). That way, we could rely on the improved semantic of having the potential '$CC' rewrite placed near the end of configure, rather than near the beginning. WDYT? > +AC_CONFIG_COMMANDS_PRE([AC_PROVIDE_IFELSE([AC_PROG_CC], > + [AC_LANG([C]) AM_PROG_CC_C_O])])dnl > AC_REQUIRE([AM_SILENT_RULES])dnl > dnl The testsuite driver may need to know about EXEEXT, so add the > dnl 'am__EXEEXT' conditional if _AM_COMPILER_EXEEXT was seen. This Thanks, Stefano
