Paul Eggert <eggert@xxxxxxxxxxx> writes: > This doesn't let you say "I want either c89 or c99, but not c11". That's right, I tried only the very simplest thing. Providing a list makes sense, thoguh. What should the interface be? AC_C_STANDARD_VERSION([c99 c89]) looks reasonable to me; list in order of preference, and whitespace separation. That's consistent with AC_PROG_CC. But that means that AC_C_STANDARD_VERSION([c89 c99]) is a bit meaningless; if compiler has c89, that's what will be used, and if it doesn't have c89, it won't have c99 either. (Alternative: Let autoconf automatically sort the list and test for the "largest" language on the list first. That may be a bit overengineered, though). I considered trying this out, but then there's some impedance mismatch between the whitespace separated list to AC_C_STANDARD_VERSION, and the comma-separated list required by m4_map. Certainly doable, but what's the easiest way to transform [c99 c89] into [99, 89] ? >> + m4_ifdef([_AC_C_STANDARD_VERSION_LIST], >> + [m4_fatal([AC_PROG_C_STANDARD_VERSION should only be used once], 1)]) > > Why have this check? I figured the user should get some error message if using AC_C_STANDARD_VERSION too late, e.g., after some AC_FOO that implicitly uses AC_PROG_CC, which will also trigger this check. Not sure of m4_fatal is the right way to signals error to the user, though. (And error message could be improved). > How about something simpler, like replacing this: > > m4_map([_AC_PROG_CC_STDC_EDITION_TRY], [[11], [99], [89]])]) > > with this: > > m4_map([_AC_PROG_CC_STDC_EDITION_TRY], > [m4_default([_AC_C_STANDARD_VERSION_LIST], > [[11], [99], [89]])]) I looked at m4_default, and it looked to me like it checks for empty string, not undef:ed m4 symbol. If _AC_C_STANDARD_VERSION_LIST is undefined, I concluded that m4_default([_AC_C_STANDARD_VERSION_LIST], whatever) just expands to the text _AC_C_STANDARD_VERSION_LIST. So I think we need _AC_C_STANDARD_VERSION_LIST to always be defined. Not sure where that definition should go, if not in _AC_PROG_CC_STDC_EDITION itself, but whwreever it is moved, I suspect it would be simpler to jsut make that definition assign the default value rather than the empty list needed for m4_default to work as intended. > and not bothering to check for allowed or duplicated version lists? Skipping that could make implementation a bit simpler, I guess, at the cost of less clear user error messages. Regards, /Niels -- Niels Möller. PGP key CB4962D070D77D7FCB8BA36271D8F1FF368C6677. Internet email is subject to wholesale government surveillance.
