lfs-book/chapter06/aboutdebug.xml

<sect1 id="ch06-aboutdebug">
<title>About debugging symbols</title>

<para>
Most programs and libraries by default are compiled with debugging
symbols and optimizing level 2 (gcc options -g and -O2) and are compiled
for a specific CPU. On Intel platforms software is compiled for i386
processors by default. If a user doesn't wish to run software on other
machines other than his own, he might want to change the default
compiler options so that they will be compiled with a higher
optimization level, no debugging symbols and generate code for his 
specific architecture. Let me first explain what debugging symbols
are.
</para>

<para>
A program compiled with debugging symbols means a user can run a program or 
library through a debugger and the debugger's output will be user friendlier. 
These debugging symbols also enlarge the program or library significantly. 
</para>

<para>
To remove debugging symbols from a binary (must be an a.out or ELF binary)
run <userinput>strip --strip-debug filename</userinput>. A user can use wild
 cards
if he needs to strip debugging symbols from multiple files (use something like
strip --strip-debug $LFS/usr/bin/*). Another, easier, options is just
not to compile programs with debugging symbols. Most people will probably
never use a debugger on software, so by leaving those symbols out 
a lot of diskspace can be saved.
</para>

<para>
Before someone wonders if these debugging symbols would make a big difference, 
here are some statistics:
</para>

<itemizedlist>

<listitem><para>
        A dynamic Bash binary with debugging symbols: 1.2MB
</para></listitem>

<listitem><para>
        A dynamic Bash binary without debugging symbols: 478KB
</para></listitem>

<listitem><para>
        /lib and /usr/lib (glibc and gcc files) with debugging
                symbols: 87MB
</para></listitem>

<listitem><para>
        /lib and /usr/lib (glibc and gcc files) without
                debugging symbols: 16MB
</para></listitem>

</itemizedlist>

<para>
Sizes may vary depending on which compiler was used and which C library
version was used to link dynamic programs against, but results will be
similar if a user compares programs with and without debugging symbols. After
I was done with this chapter and stripped all debugging symbols from all LFS
binaries and libraries I regained a little over 102 MB of disk space. Quite
the difference.
</para>

</sect1>