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doc/debugging_with_gdb: format & content update

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R=adg, lvd
CC=golang-dev
https://golang.org/cl/5845065
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Shenghou Ma 2012-03-21 00:42:53 +08:00
parent 8521811cde
commit 9dbfda5857
1 changed files with 39 additions and 38 deletions
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doc/debugging_with_gdb.html
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@ -13,13 +13,14 @@ Besides this overview you might want to consult the
<p>
When you compile and link your Go programs with the <code>gc</code> toolchain
on Linux, Mac OSX or FreeBSD, the resulting binaries contain DWARFv3
debugging information that recent versions (>7.1) of the GDB debugger can
on Linux, Mac OS X or FreeBSD, the resulting binaries contain DWARFv3
debugging information that recent versions (&gt;7.1) of the GDB debugger can
use to inspect a live process or a core dump.
</p>
<p>
Pass the <code>'-s'</code> flag to the linker to omit the debug information.
Pass the <code>'-s'</code> flag to the linker to omit the debug information
(for example, <code>go build -ldflags "-s" prog.go</code>).
</p>
@ -28,7 +29,7 @@ Pass the <code>'-s'</code> flag to the linker to omit the debug information.
<ul>
<li>
Show file and line number for code
and set breakpoints:
, set breakpoints and disassemble:
<pre>(gdb) <b>list</b>
(gdb) <b>list <i>line</i></b>
(gdb) <b>list <i>file.go</i>:<i>line</i></b>
@ -37,7 +38,7 @@ and set breakpoints:
(gdb) <b>disas</b></pre>
</li>
<li>
Unwind stack frames:
Show backtraces and unwind stack frames:
<pre>(gdb) <b>bt</b>
(gdb) <b>frame <i>n</i></b></pre>
</li>
@ -101,7 +102,7 @@ the Go source distribution. It depends on some special magic types
<code>runtime.g</code>) that the linker
(<a href="/src/cmd/ld/dwarf.c">src/cmd/ld/dwarf.c</a>) ensures are described in
the DWARF code.
</ines
</p>
<p>
If you're interested in what the debugging information looks like, run
@ -128,26 +129,26 @@ the form <code>pkg.(*MyType).Meth</code>.
<p>
In this tutorial we will inspect the binary of the
<a href="/pkg/regexp/">regexp</a> package's unit tests. To build the binary,
change to <code>$GOROOT/src/pkg/regexp</code> and run <code>gotest</code>.
This should produce an executable file named <code>6.out</code>.
change to <code>$GOROOT/src/pkg/regexp</code> and run <code>go test -c</code>.
This should produce an executable file named <code>regexp.test</code>.
</p>
<h3 id="Getting_Started">Getting Started</h3>
<p>
Launch GDB, debugging <code>6.out</code>:
Launch GDB, debugging <code>regexp.test</code>:
</p>
<pre>
$ <b>gdb 6.out</b>
$ <b>gdb regexp.test</b>
GNU gdb (GDB) 7.2-gg8
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv 3+: GNU GPL version 3 or later &lt;http://gnu.org/licenses/gpl.html&gt;
Type "show copying" and "show warranty" for licensing/warranty details.
This GDB was configured as "x86_64-linux".
Reading symbols from /home/user/go/src/pkg/regexp/6.out...
Reading symbols from /home/user/go/src/pkg/regexp/regexp.test...
done.
Loading Go Runtime support.
(gdb)
@ -164,7 +165,7 @@ pass your <code>$GOROOT</code> with the <code>'-d'</code> flag:
</p>
<pre>
$ <b>gdb 6.out -d $GOROOT</b>
$ <b>gdb regexp.test -d $GOROOT</b>
</pre>
<p>
@ -217,14 +218,13 @@ package is known to GDB as <code>'regexp.Compile'</code>.
<p>
Methods must be qualified with the name of their receiver types. For example,
the <code>*Regexp</code> type’s <code>doParse</code> method is known as
<code>'regexp.*Regexp.doParse'</code>. (Note that the second dot is a "middot,"
an artifact of Go’s internal representation of methods.)
the <code>*Regexp</code> type’s <code>String</code> method is known as
<code>'regexp.(*Regexp).String'</code>.
</p>
<p>
Variables that shadow other variables are magically suffixed with a number in the debug info.
Variables referenced by closures will appear as pointers magically prefixed with '&amp'.
Variables referenced by closures will appear as pointers magically prefixed with '&amp;'.
</p>
<h3 id="Setting_breakpoints">Setting breakpoints</h3>
@ -244,7 +244,7 @@ Run the program:
<pre>
(gdb) <b>run</b>
Starting program: /home/lvd/g/src/pkg/regexp/6.out
Starting program: /home/user/go/src/pkg/regexp/regexp.test
Breakpoint 1, regexp.TestFind (t=0xf8404a89c0) at /home/user/go/src/pkg/regexp/find_test.go:148
148 func TestFind(t *testing.T) {
@ -287,16 +287,18 @@ The other goroutine, number 1, is stuck in <code>runtime.gosched</code>, blocked
<pre>
(gdb) <b>goroutine 1 bt</b>
#0 0x000000000040facb in runtime.gosched () at /home/lvd/g/src/pkg/runtime/proc.c:873
#0 0x000000000040facb in runtime.gosched () at /home/user/go/src/pkg/runtime/proc.c:873
#1 0x00000000004031c9 in runtime.chanrecv (c=void, ep=void, selected=void, received=void)
at /home/lvd/g/src/pkg/runtime/chan.c:342
#2 0x0000000000403299 in runtime.chanrecv1 (t=void, c=void) at/home/lvd/g/src/pkg/runtime/chan.c:423
#3 0x000000000043075b in testing.RunTests (matchString={void (struct string, struct string, bool *, error *)} 0x7ffff7f9ef60, tests= []testing.InternalTest = {...}) at /home/lvd/g/src/pkg/testing/testing.go:201
#4 0x00000000004302b1 in testing.Main (matchString={void (struct string, struct string, bool *, error *)} 0x7ffff7f9ef80, tests= []testing.InternalTest = {...}, benchmarks= []testing.InternalBenchmark = {...})
at /home/lvd/g/src/pkg/testing/testing.go:168
#5 0x0000000000400dc1 in main.main () at /home/lvd/g/src/pkg/regexp/_testmain.go:98
#6 0x00000000004022e7 in runtime.mainstart () at /home/lvd/g/src/pkg/runtime/amd64/asm.s:78
#7 0x000000000040ea6f in runtime.initdone () at /home/lvd/g/src/pkg/runtime/proc.c:243
at /home/user/go/src/pkg/runtime/chan.c:342
#2 0x0000000000403299 in runtime.chanrecv1 (t=void, c=void) at/home/user/go/src/pkg/runtime/chan.c:423
#3 0x000000000043075b in testing.RunTests (matchString={void (struct string, struct string, bool *, error *)}
0x7ffff7f9ef60, tests= []testing.InternalTest = {...}) at /home/user/go/src/pkg/testing/testing.go:201
#4 0x00000000004302b1 in testing.Main (matchString={void (struct string, struct string, bool *, error *)}
0x7ffff7f9ef80, tests= []testing.InternalTest = {...}, benchmarks= []testing.InternalBenchmark = {...})
at /home/user/go/src/pkg/testing/testing.go:168
#5 0x0000000000400dc1 in main.main () at /home/user/go/src/pkg/regexp/_testmain.go:98
#6 0x00000000004022e7 in runtime.mainstart () at /home/user/go/src/pkg/runtime/amd64/asm.s:78
#7 0x000000000040ea6f in runtime.initdone () at /home/user/go/src/pkg/runtime/proc.c:243
#8 0x0000000000000000 in ?? ()
</pre>
@ -307,7 +309,7 @@ The stack frame shows we’re currently executing the <code>regexp.TestFind</cod
<pre>
(gdb) <b>info frame</b>
Stack level 0, frame at 0x7ffff7f9ff88:
rip = 0x425530 in regexp.TestFind (/home/lvd/g/src/pkg/regexp/find_test.go:148);
rip = 0x425530 in regexp.TestFind (/home/user/go/src/pkg/regexp/find_test.go:148);
saved rip 0x430233
called by frame at 0x7ffff7f9ffa8
source language minimal.
@ -346,12 +348,12 @@ $1 = (struct testing.T *) 0xf840688b60
$1 = (struct testing.T *) 0xf840688b60
(gdb) p *t
$2 = {errors = "", failed = false, ch = 0xf8406f5690}
(gdb) p *t->ch
$3 = struct hchan<*testing.T>
(gdb) p *t-&gt;ch
$3 = struct hchan&lt;*testing.T&gt;
</pre>
<p>
That <code>struct hchan<*testing.T></code> is the runtime-internal representation of a channel. It is currently empty, or gdb would have pretty-printed it's contents.
That <code>struct hchan&lt;*testing.T&gt;</code> is the runtime-internal representation of a channel. It is currently empty, or gdb would have pretty-printed it's contents.
</p>
<p>
@ -384,7 +386,7 @@ We can step into the <code>String</code>function call with <code>"s"</code>:
<pre>
(gdb) <b>s</b>
regexp.(*Regexp).String (re=0xf84068d070, noname=void) at /home/lvd/g/src/pkg/regexp/regexp.go:97
regexp.(*Regexp).String (re=0xf84068d070, noname=void) at /home/user/go/src/pkg/regexp/regexp.go:97
97 func (re *Regexp) String() string {
</pre>
@ -394,14 +396,13 @@ Get a stack trace to see where we are:
<pre>
(gdb) <b>bt</b>
(gdb) bt
#0 regexp.(*Regexp).String (re=0xf84068d070, noname=void)
at /home/lvd/g/src/pkg/regexp/regexp.go:97
at /home/user/go/src/pkg/regexp/regexp.go:97
#1 0x0000000000425615 in regexp.TestFind (t=0xf840688b60)
at /home/lvd/g/src/pkg/regexp/find_test.go:151
at /home/user/go/src/pkg/regexp/find_test.go:151
#2 0x0000000000430233 in testing.tRunner (t=0xf840688b60, test=0x5747b8)
at /home/lvd/g/src/pkg/testing/testing.go:156
#3 0x000000000040ea6f in runtime.initdone () at /home/lvd/g/src/pkg/runtime/proc.c:243
at /home/user/go/src/pkg/testing/testing.go:156
#3 0x000000000040ea6f in runtime.initdone () at /home/user/go/src/pkg/runtime/proc.c:243
....
</pre>
@ -442,7 +443,7 @@ you can look inside the runtime representation to do that (tab completion helps
(gdb) <b>p slc</b>
$11 = []int = {0, 0}
(gdb) <b>p slc-&gt</b><i>&ltTAB&gt</i>
(gdb) <b>p slc-&gt;</b><i>&lt;TAB&gt;</i>
array slc len
(gdb) <b>p slc->array</b>
$12 = (int *) 0xf84057af00
@ -463,7 +464,7 @@ $24 = 4
</pre>
<p>
Channels and maps are 'reference' types, which gdb shows as pointers to C++-like types <code>hash&ltint,string&gt*</code>. Dereferencing will trigger prettyprinting
Channels and maps are 'reference' types, which gdb shows as pointers to C++-like types <code>hash&lt;int,string&gt;*</code>. Dereferencing will trigger prettyprinting
</p>
<p>