Re: Specifying Flag Order?

[Jordan H.]

I think I'm getting close to understanding what's going on with 
configure.ac and Makefile. Here's what I understand...
I used to think of them separately...that `./configure` just warns the 
user of a library they're missing; now I'm realizing `./configure` 
(generated from `configure.ac`, of course) can configure variable to be 
used in Makefile, like this:

    SOME_IF_MACRO( [ test_for_something ], [ TEST_VARIABLE = 
something_if_true ], [ TEST_VARIABLE = something_else_if_false ] )

And then I can use that variable in my Makefile.am...

    myprog_CPPFLAGS += $(TEST_VARIABLE) ...

Is that correct? I guess I'm mainly writing this to think out loud and 
also to help anyone searching the nets for automake help.

On Thu 23 May 2013 07:24:04 AM PDT, Jordan H. wrote:
>
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> Yes, I'll try that. Thank you.
> I'm still trying to get a hang of what all the macros and variables
> mean...I understand the basic syntax, at least.
> While we're on the topic, any resources out there to help someone get a
> handle on vars/macros? I see in the automake manual an entire index but
> it doesn't seem to be beginner-friendly.
> Thanks.
>
> Luke Mewburn:
>> On Wed, May 22, 2013 at 04:46:36PM -0700, Jordan H. wrote:
>>   | I'm using mysql in a program. Here is a snipped of my Makefile.am:
>>   |
>>   |     project_LDADD += -lboost_thread
>>   |     project_LDADD += -lboost_regex
>>   |     project_LDADD += -lboost_system
>>   |
>>   |     AM_LDFLAGS = -L/usr/local/lib
>>   |     AM_LDFLAGS += `mysql_config --libs_r`
>>   |     AM_LDFLAGS += `mysql_config --include`
>>   |     AM_LDFLAGS += -std=c++0x
>>   |     AM_LDFLAGS += `mysql_config --cflags`
>>   |
>>   | When I compile the program, automake generated:
>>   |
>>   |     g++  -g -O2 -L/usr/local/lib `mysql_config --libs_r` `mysql_config
>>   | --include` -std=c++0x
>>   |     `mysql_config --cflags`  -o /[ ... a bunch of .o files ... ]/
>>   | -lboost_thread -lboost_regex
>>   |     -lboost_system
>>   |
>>   | As expected, since g++ needs linker flags at the end I get a bunch of
>>   | compile errors saying the `mysql_*` functions don't exist. How do I
>>   | specify for the linker flags to go at the end? I tried to put them in
>>   | the project_LDADD macro but automake complained:
>>   |
>>   |     Makefile.am:13: linker flags such as `--libs_r`' belong in
>>   | `project_LDFLAGS
>>   |
>>   | Which got me back to square one. I must be doing something wrong. Any
>>   | ideas? This has been bugging me for days. Thanks in advance.
>>
>> Hi Jordan,
>>
>> I define some automake substition variables in configure.ac as part
>> of the checks for MySQL:
>>
>>     # Look for mysql via the presence of 'mysql_config' or 'mysql_config5'
>>     #
>>     AC_PATH_PROGS([TOOL_MYSQL_CONFIG], [mysql_config mysql_config5], [],
>>               [$PATH:/opt/local/bin])
>>     AS_IF([test -n "$TOOL_MYSQL_CONFIG"],
>>           [MYSQL_CFLAGS=`$TOOL_MYSQL_CONFIG --cflags`
>>            MYSQL_LIBS=`$TOOL_MYSQL_CONFIG --libs_r`
>>            MYSQL_VERSION=`$TOOL_MYSQL_CONFIG --version`],
>>           [AC_MSG_ERROR([missing program 'mysql_config'; is 'mysql' or
> 'MySQL-devel' installed?])])
>>
>>     WANT_MYSQL_VERSION=5.1.55
>>
>>     AC_MSG_CHECKING([for mysql >= $WANT_MYSQL_VERSION])
>>     AS_VERSION_COMPARE([$MYSQL_VERSION], [$WANT_MYSQL_VERSION],
>>          [AC_MSG_RESULT([no])
>>           AC_MSG_FAILURE([mysql $MYSQL_VERSION is too old, need
> $WANT_MYSQL_VERSION])])
>>     AC_MSG_RESULT([yes])
>>
>>     AC_SUBST([MYSQL_CFLAGS])
>>     AC_SUBST([MYSQL_LIBS])
>>     AC_PATH_PROGS([TOOL_MYSQL], [mysql mysql5], [],
>>               [$PATH:/opt/local/bin])
>>     AS_IF([test -n "$TOOL_MYSQL"],
>>           [:],
>>           [AC_MSG_ERROR([missing program 'mysql'; is 'mysql' or
> 'MySQL-client-community' installed?])])
>>
>>
>> I then use these in the Makefile.am as:
>>
>>     prog_CPPFLAGS += $(MYSQL_CFLAGS)
>>     prog_LDADD += $(MYSQL_LIBS)
>>
>> (As an aside, you probably don't want includes and cflags in LDFLAGS)
>>
>> I don't bother with `mysql_config --include`
>>
>>
>> Feel free to reuse those snippets as you like.
>>
>>
>> I hope that's useful.
>>
>>
>> Regards,
>> Luke.
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