[erlang-questions] How to configure otp for a debug build (with otp_build)?

[Winston Smith]

On Fri, Sep 9, 2011 at 4:47 AM, Gustav Simonsson
<gustav.simonsson@REDACTED> wrote:
> There is a line with "CFLAGS=" in the xcomp file where you can add flags to gcc,
> such as debug options found in
> http://gcc.gnu.org/onlinedocs/gcc-4.6.1/gcc/Debugging-Options.html#Debugging-Options

I think there's more to it than that.  At the very least, you need to
swap the -O2 (or whatever Erlang builds with by default) for -g and
also define -DDEBUG, but there's also the fact that you don't want
symbols stripped for a debug build.  So a debug version is something
that really has to be "embraced" by otp_build.   After some digging, I
found the following notes:

http://www.erlang.org/doc/installation_guide/INSTALL.html#How-to-Build-a-Debug-Enabled-Erlang-RunTime-System

These basically that say that after configuring to go into
$ERL_TOP/erts/emulator and run:

make debug FLAVOR=plain


But for an xcomp (cross compile) configuration, this simply built a
debug version of the host system's Erlang (not the target systems
which is what I need).  Note that in this case, the host system is my
Ubuntu 11.04 x64 system, the target is my AVR32 Linux board.  I found
that if you invoke make as follows, then it'll build a debug version
for the target (not the host!):

make debug FLAVOR=plain TARGET=avr32-atmel-linux-gnu


Since my segmentation fault seems to be related to inet_gethost, I
found that this wasn't building a debug version of inet_gethost, so I
also had to go into $ERL_TOP/erts/etc/common and run the same make
command, again as follows:

make debug FLAVOR=plain TARGET=avr32-atmel-linux-gnu


In order to get a debug version of inet_gethost.  Note that this
make-debug invocation does in fact produce unstripped debug
executables which is a necessity for debugging.

I don't know how successful this was/will be [in terms of tracking
down my segmentation fault], but I'm about to start testing it now
...!

Thanks!


Winston.