RFR: JDK-8146995 Introduce named arguments in configure

[Erik Joelsson]

The implementation of the m4 black magic macro certainly looks scary. I 
was able to understand the first conditional block. I did apply and try 
the patch and verified that -stack-protector was added to cflags when 
setting slowdebug. The readability of the macro calls are definitely 
much more understandable. I like it. Looks good.

/Erik

On 2016-01-13 15:43, Magnus Ihse Bursie wrote:
> Similar to how we use named argument in makefiles, we should support 
> named arguments in the configure scripts. This is possible using some 
> m4 black magic.
>
> My long-term goal with this is to provide readable functions for 
> handling common patterns, like parsing --with arguments and doing 
> proper action depending on the value of the flag.
>
> Since the m4 logic is hairy, to say the least, I chose to pick a more 
> simple function to use as test bench for getting the actual m4 
> underpinning to work.
>
> The essence of this change can be seen here:
>
> - FLAGS_COMPILER_CHECK_ARGUMENTS([$STACK_PROTECTOR_CFLAG], [], 
> [STACK_PROTECTOR_CFLAG=""])
> + FLAGS_COMPILER_CHECK_ARGUMENTS(ARGUMENT: [$STACK_PROTECTOR_CFLAG], 
> IF_FALSE: [STACK_PROTECTOR_CFLAG=""])
>
>
> Just like in our Setup* macros in make, now it is possible to use 
> named arguments in autoconf macros. Named arguments can come in any 
> order. The framework will verify that only known arguments is allowed 
> in. It is also possible to mark an argument as compulsory (by 
> prefixing it with *). The framework will verify that all required 
> arguments are present.
>
> Don't ask me to explain the finer points of BASIC_DEFUN_NAMED. :) 
> m4/autoconf is non-trivial to get correct, with few debugging 
> possibilities and sparse documentation. There's a lot of trial and 
> error behind this final version. :-&
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8146995
> WebRev: 
> http://cr.openjdk.java.net/~ihse/JDK-8146995-named-arguments-in-configure/webrev.01
>
> /Magnus
>