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                        <h1><a class="header" href="#gdb1" id="gdb1">gdb(1)</a></h1>
<h1><a class="header" href="#cli" id="cli">CLI</a></h1>
<pre><code class="language-markdown">  gdb [opts] [prg [-c coredump | -p pid]]
  gdb [opts] --args prg &lt;prg-args&gt;
    opts:
      -p &lt;pid&gt;        attach to pid
      -c &lt;coredump&gt;   use &lt;coredump&gt;
      -x &lt;file&gt;       execute script &lt;file&gt; before prompt
      -ex &lt;cmd&gt;       execute command &lt;cmd&gt; before prompt
      --tty &lt;tty&gt;     set I/O tty for debugee
</code></pre>
<h1><a class="header" href="#interactive-usage" id="interactive-usage">Interactive usage</a></h1>
<h2><a class="header" href="#misc" id="misc">Misc</a></h2>
<pre><code class="language-markdown">  tty &lt;tty&gt;
          Set &lt;tty&gt; as tty for debugee.
          Make sure nobody reads from target tty, easiest is to spawn a shell
          and run following in target tty:
          &gt; while true; do sleep 1024; done

  sharedlibrary [&lt;regex&gt;]
          Load symbols of shared libs loaded by debugee. Optionally use &lt;regex&gt;
          to filter libs for symbol loading.

  display [/FMT] &lt;expr&gt;
          Print &lt;expr&gt; every time debugee stops. Eg print next instr, see
          examples below.

  undisplay [&lt;num&gt;]
          Delete display expressions either all or one referenced by &lt;num&gt;.

  info display
          List display expressions.
</code></pre>
<h2><a class="header" href="#breakpoints" id="breakpoints">Breakpoints</a></h2>
<pre><code class="language-markdown">  break [-qualified] &lt;sym&gt; thread &lt;tnum&gt;
          Set a breakpoint only for a specific thread.
          -qualified: Treat &lt;sym&gt; as fully qualified symbol (quiet handy to set
          breakpoints on C symbols in C++ contexts)

  break &lt;sym&gt; if &lt;cond&gt;
          Set conditional breakpoint (see examples below).

  delete [&lt;num&gt;]
          Delete breakpoint either all or one referenced by &lt;num&gt;.

  info break
          List breakpoints.

  cond &lt;bp&gt; &lt;cond&gt;
          Make existing breakpoint &lt;bp&gt; conditional with &lt;cond&gt;.

  tbreak
          Set temporary breakpoint, will be deleted when hit.
          Same syntax as `break`.

  rbreak &lt;regex&gt;
          Set breakpoints matching &lt;regex&gt;, where matching internally is done
          on: .*&lt;regex&gt;.*

  command [&lt;bp_list&gt;]
          Define commands to run after breakpoint hit. If &lt;bp_list&gt; is not
          specified attach command to last created breakpoint. Command block
          terminated with 'end' token.

          &lt;bp_list&gt;: Space separates list, eg 'command 2 5-8' to run command
          for breakpoints: 2,5,6,7,8.
</code></pre>
<h2><a class="header" href="#inspection" id="inspection">Inspection</a></h2>
<pre><code class="language-markdown">  info functions [&lt;regex&gt;]
          List functions matching &lt;regex&gt;. List all functions if no &lt;regex&gt;
          provided.

  info variables [&lt;regex&gt;]
          List variables matching &lt;regex&gt;. List all variables if no &lt;regex&gt;
          provided.
</code></pre>
<h2><a class="header" href="#signal-handling" id="signal-handling">Signal handling</a></h2>
<pre><code class="language-markdown">  info handle [&lt;signal&gt;]
          Print how to handle &lt;signal&gt;. If no &lt;signal&gt; specified print for all
          signals.

  handle &lt;signal&gt; &lt;action&gt;
          Configure how gdb handles &lt;signal&gt; sent to debugee.
          &lt;action&gt;:
            stop/nostop       Catch signal in gdb and break.
            print/noprint     Print message when gdb catches signal.
            pass/nopass       Pass signal down to debugee.

  catch signal &lt;signal&gt;
          Create a catchpoint for &lt;signal&gt;.
</code></pre>
<h2><a class="header" href="#source-file-locations" id="source-file-locations">Source file locations</a></h2>
<pre><code class="language-markdown">  dir &lt;path&gt;
          Add &lt;path&gt; to the beginning of the searh path for source files.

  show dir
          Show current search path.

  set substitute-path &lt;from&gt; &lt;to&gt;
          Add substitution rule checked during source file lookup.

  show substitute-path
          Show current substitution rules.
</code></pre>
<h2><a class="header" href="#configuration" id="configuration">Configuration</a></h2>
<pre><code class="language-markdown">  set follow-fork-mode &lt;child | parent&gt;
          Specify which process to follow when debuggee makes a fork(2)
          syscall.

  set pagination &lt;on | off&gt;
          Turn on/off gdb's pagination.

  set breakpoint pending &lt;on | off | auto&gt;
          on: always set pending breakpoints.
          off: error when trying to set pending breakpoints.
          auto: interatively query user to set breakpoint.

  set print pretty &lt;on | off&gt;
          Turn on/off pertty printing of structures.

  set logging &lt;on | off&gt;
          Enable output logging to file (default gdb.txt).

  set logging file &lt;fname&gt;
          Change output log file to &lt;fname&gt;

  set logging redirect &lt;on/off&gt;
          on: only log to file.
          off: log to file and tty.
</code></pre>
<h1><a class="header" href="#user-commands-macros" id="user-commands-macros">User commands (macros)</a></h1>
<p>Gdb allows to create &amp; document user commands as follows:</p>
<pre><code class="language-markdown">  define &lt;cmd&gt;
    # cmds
  end

  document &lt;cmd&gt;
    # docu
  end
</code></pre>
<p>To get all user commands or documentations one can use:</p>
<pre><code class="language-markdown">  help user-defined
  help &lt;cmd&gt;
</code></pre>
<h1><a class="header" href="#hooks" id="hooks">Hooks</a></h1>
<p>Gdb allows to create two types of command <code>hooks</code></p>
<ul>
<li><code>hook-</code> will be run before <code>&lt;cmd&gt;</code></li>
<li><code>hookpost-</code> will be run after <code>&lt;cmd&gt;</code></li>
</ul>
<pre><code class="language-markdown">  define hook-&lt;cmd&gt;
    # cmds
  end

  define hookpost-&lt;cmd&gt;
    # cmds
  end
</code></pre>
<h1><a class="header" href="#examples" id="examples">Examples</a></h1>
<h2><a class="header" href="#automatically-print-next-instr" id="automatically-print-next-instr">Automatically print next instr</a></h2>
<p>When ever the debugee stops automatically print the memory at the current
instruction pointer (<code>$rip</code> x86) and format as instruction <code>/i</code>.</p>
<pre><code class="language-markdown">  # rip - x86
  display /i $rip

  # step instruction, after the step the next instruction is automatically printed
  si
</code></pre>
<h2><a class="header" href="#conditional-breakpoints" id="conditional-breakpoints">Conditional breakpoints</a></h2>
<p>Create conditional breakpoints for a function <code>void foo(int i)</code> in the debugee.</p>
<pre><code class="language-markdown">  # Create conditional breakpoint
  b foo if i == 42

  b foo     # would create bp 2
  # Make existing breakpoint conditional
  cond 2 if i == 7
</code></pre>
<h2><a class="header" href="#catch-sigsegv-and-execute-commands" id="catch-sigsegv-and-execute-commands">Catch SIGSEGV and execute commands</a></h2>
<p>This creates a <code>catchpoint</code> for the <code>SIGSEGV</code> signal and attached the <code>command</code>
to it.</p>
<pre><code class="language-markdown">  catch signal SIGSEGV
  command
    bt
    c
  end
</code></pre>
<h2><a class="header" href="#run-backtrace-on-thread-1-batch-mode" id="run-backtrace-on-thread-1-batch-mode">Run <code>backtrace</code> on thread 1 (batch mode)</a></h2>
<pre><code class="language-markdown">  gdb --batch -ex 'thread 1' -ex 'bt' -p &lt;pid&gt;
</code></pre>
<h2><a class="header" href="#script-gdb-for-automating-debugging-sessions" id="script-gdb-for-automating-debugging-sessions">Script gdb for automating debugging sessions</a></h2>
<p>To script gdb add commands into a file and pass it to gdb via <code>-x</code>.
For example create <code>run.gdb</code>:</p>
<pre><code class="language-markdown">  set pagination off

  break mmap
  command
    info reg rdi rsi rdx
    bt
    c
  end

  #initial drop
  c
</code></pre>
<p>This script can be used as:</p>
<pre><code class="language-markdown">  gdb --batch -x ./run.gdb -p &lt;pid&gt;
</code></pre>
<h1><a class="header" href="#know-bugs" id="know-bugs">Know Bugs</a></h1>
<h2><a class="header" href="#workaround-command--finish-bug" id="workaround-command--finish-bug">Workaround <code>command + finish</code> bug</a></h2>
<p>When using <code>finish</code> inside a <code>command</code> block, commands after <code>finish</code> are not
executed. To workaround that bug one can create a wrapper function which calls
<code>finish</code>.</p>
<pre><code class="language-markdown">  define handler
    bt
    finish
    info reg rax
  end

  command
    handler
  end
</code></pre>

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                        <h1><a class="header" href="#gdb1" id="gdb1">gdb(1)</a></h1>
<h1><a class="header" href="#cli" id="cli">CLI</a></h1>
<pre><code class="language-markdown">  gdb [opts] [prg [-c coredump | -p pid]]
  gdb [opts] --args prg &lt;prg-args&gt;
    opts:
      -p &lt;pid&gt;        attach to pid
      -c &lt;coredump&gt;   use &lt;coredump&gt;
      -x &lt;file&gt;       execute script &lt;file&gt; before prompt
      -ex &lt;cmd&gt;       execute command &lt;cmd&gt; before prompt
      --tty &lt;tty&gt;     set I/O tty for debugee
</code></pre>
<h1><a class="header" href="#interactive-usage" id="interactive-usage">Interactive usage</a></h1>
<h2><a class="header" href="#misc" id="misc">Misc</a></h2>
<pre><code class="language-markdown">  tty &lt;tty&gt;
          Set &lt;tty&gt; as tty for debugee.
          Make sure nobody reads from target tty, easiest is to spawn a shell
          and run following in target tty:
          &gt; while true; do sleep 1024; done

  sharedlibrary [&lt;regex&gt;]
          Load symbols of shared libs loaded by debugee. Optionally use &lt;regex&gt;
          to filter libs for symbol loading.

  display [/FMT] &lt;expr&gt;
          Print &lt;expr&gt; every time debugee stops. Eg print next instr, see
          examples below.

  undisplay [&lt;num&gt;]
          Delete display expressions either all or one referenced by &lt;num&gt;.

  info display
          List display expressions.
</code></pre>
<h2><a class="header" href="#breakpoints" id="breakpoints">Breakpoints</a></h2>
<pre><code class="language-markdown">  break [-qualified] &lt;sym&gt; thread &lt;tnum&gt;
          Set a breakpoint only for a specific thread.
          -qualified: Treat &lt;sym&gt; as fully qualified symbol (quiet handy to set
          breakpoints on C symbols in C++ contexts)

  break &lt;sym&gt; if &lt;cond&gt;
          Set conditional breakpoint (see examples below).

  delete [&lt;num&gt;]
          Delete breakpoint either all or one referenced by &lt;num&gt;.

  info break
          List breakpoints.

  cond &lt;bp&gt; &lt;cond&gt;
          Make existing breakpoint &lt;bp&gt; conditional with &lt;cond&gt;.

  tbreak
          Set temporary breakpoint, will be deleted when hit.
          Same syntax as `break`.

  rbreak &lt;regex&gt;
          Set breakpoints matching &lt;regex&gt;, where matching internally is done
          on: .*&lt;regex&gt;.*

  command [&lt;bp_list&gt;]
          Define commands to run after breakpoint hit. If &lt;bp_list&gt; is not
          specified attach command to last created breakpoint. Command block
          terminated with 'end' token.

          &lt;bp_list&gt;: Space separates list, eg 'command 2 5-8' to run command
          for breakpoints: 2,5,6,7,8.
</code></pre>
<h2><a class="header" href="#inspection" id="inspection">Inspection</a></h2>
<pre><code class="language-markdown">  info functions [&lt;regex&gt;]
          List functions matching &lt;regex&gt;. List all functions if no &lt;regex&gt;
          provided.

  info variables [&lt;regex&gt;]
          List variables matching &lt;regex&gt;. List all variables if no &lt;regex&gt;
          provided.
</code></pre>
<h2><a class="header" href="#signal-handling" id="signal-handling">Signal handling</a></h2>
<pre><code class="language-markdown">  info handle [&lt;signal&gt;]
          Print how to handle &lt;signal&gt;. If no &lt;signal&gt; specified print for all
          signals.

  handle &lt;signal&gt; &lt;action&gt;
          Configure how gdb handles &lt;signal&gt; sent to debugee.
          &lt;action&gt;:
            stop/nostop       Catch signal in gdb and break.
            print/noprint     Print message when gdb catches signal.
            pass/nopass       Pass signal down to debugee.

  catch signal &lt;signal&gt;
          Create a catchpoint for &lt;signal&gt;.
</code></pre>
<h2><a class="header" href="#source-file-locations" id="source-file-locations">Source file locations</a></h2>
<pre><code class="language-markdown">  dir &lt;path&gt;
          Add &lt;path&gt; to the beginning of the searh path for source files.

  show dir
          Show current search path.

  set substitute-path &lt;from&gt; &lt;to&gt;
          Add substitution rule checked during source file lookup.

  show substitute-path
          Show current substitution rules.
</code></pre>
<h2><a class="header" href="#configuration" id="configuration">Configuration</a></h2>
<pre><code class="language-markdown">  set follow-fork-mode &lt;child | parent&gt;
          Specify which process to follow when debuggee makes a fork(2)
          syscall.

  set pagination &lt;on | off&gt;
          Turn on/off gdb's pagination.

  set breakpoint pending &lt;on | off | auto&gt;
          on: always set pending breakpoints.
          off: error when trying to set pending breakpoints.
          auto: interatively query user to set breakpoint.

  set print pretty &lt;on | off&gt;
          Turn on/off pertty printing of structures.

  set logging &lt;on | off&gt;
          Enable output logging to file (default gdb.txt).

  set logging file &lt;fname&gt;
          Change output log file to &lt;fname&gt;

  set logging redirect &lt;on/off&gt;
          on: only log to file.
          off: log to file and tty.
</code></pre>
<h1><a class="header" href="#user-commands-macros" id="user-commands-macros">User commands (macros)</a></h1>
<p>Gdb allows to create &amp; document user commands as follows:</p>
<pre><code class="language-markdown">  define &lt;cmd&gt;
    # cmds
  end

  document &lt;cmd&gt;
    # docu
  end
</code></pre>
<p>To get all user commands or documentations one can use:</p>
<pre><code class="language-markdown">  help user-defined
  help &lt;cmd&gt;
</code></pre>
<h1><a class="header" href="#hooks" id="hooks">Hooks</a></h1>
<p>Gdb allows to create two types of command <code>hooks</code></p>
<ul>
<li><code>hook-</code> will be run before <code>&lt;cmd&gt;</code></li>
<li><code>hookpost-</code> will be run after <code>&lt;cmd&gt;</code></li>
</ul>
<pre><code class="language-markdown">  define hook-&lt;cmd&gt;
    # cmds
  end

  define hookpost-&lt;cmd&gt;
    # cmds
  end
</code></pre>
<h1><a class="header" href="#examples" id="examples">Examples</a></h1>
<h2><a class="header" href="#automatically-print-next-instr" id="automatically-print-next-instr">Automatically print next instr</a></h2>
<p>When ever the debugee stops automatically print the memory at the current
instruction pointer (<code>$rip</code> x86) and format as instruction <code>/i</code>.</p>
<pre><code class="language-markdown">  # rip - x86
  display /i $rip

  # step instruction, after the step the next instruction is automatically printed
  si
</code></pre>
<h2><a class="header" href="#conditional-breakpoints" id="conditional-breakpoints">Conditional breakpoints</a></h2>
<p>Create conditional breakpoints for a function <code>void foo(int i)</code> in the debugee.</p>
<pre><code class="language-markdown">  # Create conditional breakpoint
  b foo if i == 42

  b foo     # would create bp 2
  # Make existing breakpoint conditional
  cond 2 if i == 7
</code></pre>
<h2><a class="header" href="#catch-sigsegv-and-execute-commands" id="catch-sigsegv-and-execute-commands">Catch SIGSEGV and execute commands</a></h2>
<p>This creates a <code>catchpoint</code> for the <code>SIGSEGV</code> signal and attached the <code>command</code>
to it.</p>
<pre><code class="language-markdown">  catch signal SIGSEGV
  command
    bt
    c
  end
</code></pre>
<h2><a class="header" href="#run-backtrace-on-thread-1-batch-mode" id="run-backtrace-on-thread-1-batch-mode">Run <code>backtrace</code> on thread 1 (batch mode)</a></h2>
<pre><code class="language-markdown">  gdb --batch -ex 'thread 1' -ex 'bt' -p &lt;pid&gt;
</code></pre>
<h2><a class="header" href="#script-gdb-for-automating-debugging-sessions" id="script-gdb-for-automating-debugging-sessions">Script gdb for automating debugging sessions</a></h2>
<p>To script gdb add commands into a file and pass it to gdb via <code>-x</code>.
For example create <code>run.gdb</code>:</p>
<pre><code class="language-markdown">  set pagination off

  break mmap
  command
    info reg rdi rsi rdx
    bt
    c
  end

  #initial drop
  c
</code></pre>
<p>This script can be used as:</p>
<pre><code class="language-markdown">  gdb --batch -x ./run.gdb -p &lt;pid&gt;
</code></pre>
<h1><a class="header" href="#know-bugs" id="know-bugs">Know Bugs</a></h1>
<h2><a class="header" href="#workaround-command--finish-bug" id="workaround-command--finish-bug">Workaround <code>command + finish</code> bug</a></h2>
<p>When using <code>finish</code> inside a <code>command</code> block, commands after <code>finish</code> are not
executed. To workaround that bug one can create a wrapper function which calls
<code>finish</code>.</p>
<pre><code class="language-markdown">  define handler
    bt
    finish
    info reg rax
  end

  command
    handler
  end
</code></pre>

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