Re: AC_CHECK_PROGS and java compiler options

[John Calcote]

Hi Ralf,

Hey, thanks for the response.

On 8/22/2009 1:59 AM, Ralf Wildenhues wrote:
> Hello John,
>
> * John Calcote wrote on Fri, Aug 21, 2009 at 02:44:03AM CEST:
>    
> > I'm wondering about best practices for checking for programs like
> > the javac compiler. For instance, I currently have a line in my
> > project's configure.ac file that looks like this:
> >
> > AC_CHECK_PROGS([JAVAC], ["gcj -C -ftarget=1.4 -fsource=1.4" "guavac
> > -target 1.4 -source 1.4" "jikes -target 1.4 -source 1.4" "javac
> > -target 1.4 -source 1.4"])
> >      
> Why are you doing this?  AC_CHECK_PROGS will cut off the arguments when
> searching for the program anyway, it don't try to run the program.
>    

The reason that *I* do this is so that the program variable (JAVAC) will 
be set to the specified string (possibly prefixed with a path, if the 
skip argument is used). For example, if gcj is found in the path, then 
JAVAC should be set to "gcj -C". This is because, for gcj to act like 
Sun's javac program, you need to pass the -C option (otherwise it will 
compile Java sources to native code instead of Java byte code). But if 
none of the programs is found until the search reaches javac, then JAVAC 
should be set to just "javac".

This system was fine, when the *only* difference between programs was 
the -C option on gcj. Then it made sense to just pass -C in the search 
for gcj. But now that I need to specify target JVM and source version 
restrictions, it seems silly to pass the same set of additional command 
line options to all programs *except* gcj (which requires a slightly 
different format for these options). If they were all the same, I'd just 
add them to the JAVACFLAGS variable.

> The semantics of AC_CHECK_PROGS are purely done so that one can pass in
> variables to AC_CHECK_PROGS that are also used likewise elsewhere; but
> for the tests done by this macro, they are not relevant.
>    

Hmmm. I thought the point of being able to pass options to various 
search programs in AC_CHECK_PROGS was to be able to conform run-time 
characteristics of one of the programs to that of the others in the 
list, if options were required in order to do so. Those options are then 
pasted onto the command that's ultimately set in the variable. At least, 
that's what the comments in the macro definition appear to be telling 
the reader.

In fact, this works very well. When I use $(JAVAC) in my Makefile.am 
files, I do get the correct options passed for the first located program 
- "gcj -C -ftarget=1.4 -fsource=1.4" on my 64-bit linux system, and 
"javac -target 1.4 -source 1.4" on systems with only the Sun java 
compiler installed.

I was just asking if there's a better way to pass different options to 
different commands found by AC_CHECK_PROGS, but in fact, I can't really 
envision anything else that would work better. It just /feels/ like the 
wrong place to do what I'm trying to do.

John