How can I add LDFLAGS for bsp build?

[Joel Sherrill]

This is an application matter and it all depends on what build system you
are using.

If your build system is make, then something like this will probably work.

LDFLAGS += -lm

You may also want to ensure that the CFLAGS has the desired optimization,
debug, and warning levels selected:

CFLAGS += -Og -g -Wall
CXXFLAGS +=  -Og -g -Wall

If using waf, cmake, etc, etc, you ultimately want to produce the same
invocations of gcc but the mechanics are different.

--joel

On Fri, Jul 22, 2022 at 9:09 AM DAVE ERICKSON <daveerickson at shaw.ca> wrote:

> Hi Y.HB
>
> LDFLAGS sets both the library kind to include in the archive build but it
> also uses the -L flags to know where to look for it. The -lm can mean the
> libm.a. libm.so libm.la so it searches the LD_LIBRARY_PATH environment
> variable to find one that fits. If you want expressly to include the libm.a
> you should specify it instead of -lm. The first thing I recommend is find
> the symbols inside the Makefile configured for the .  Look for the LDFLAGS
> and then your LD_LIBRARY_PATH to see if it matches where that
> arm-rtems5/lib/libm.a is.
>
> You can even use the flag argument:  arm-rtems5/lib/libm.a or
> ./arm-rtems5/lib/libm.a to express the precise library and location to use.
>
> This is one important distinction that many people confuse about how
> automake and autoconf work: There is no "internal logic" in the autotools
> way of creating recipes for Makefiles. m4 is used for pattern processing.
> You must express what you want it to make, it won't go looking anywhere
> else than what is specified.
>
> It's not cmake, scons, or raw make. GNU Autotools creates recipe files,
> like config.status, that just hold environmental variables.
>
> DaemonDave on github.
>
> ------------------------------
> *From: *"Y. HB" <sprhawk at gmail.com>
> *To: *"rtems-users at rtems.org" <users at rtems.org>
> *Sent: *Friday, July 22, 2022 12:11:38 AM
> *Subject: *Re: How can I add LDFLAGS for bsp build?
>
> I added -lm in LDFLAGS in my custom bsps/arm/tms570/config/xxx.cfg
>
> the flag is added to compiling arguments, but it still reported undefined
> reference to 'floor', but I see there is floor symbols in the
> arm-rtems5/lib/libm.a
>
> Why is it?
>
> Thanks
>
> On Fri, Jul 22, 2022 at 1:43 PM Y. HB <sprhawk at gmail.com> wrote:
>
>> Hello
>>
>> I'm working on a custom tms570 bsp upon RTEMS 5.1, but it depends on math
>> lib (-lm), how can I add this flag to the bsp build?
>>
>> Shall I add LDFLAGS="-lm" during configure or shall I change some
>> variables in c/src/lib/libbsp/arm/xxxx/Makefile.am?
>>
>> Thanks
>>
>
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