1. 反向調試

gdb支持程序反向執行。

record??讓程序開始記錄反向調試所必要的信息

rn :?reverse next

rc: reverse continue ，Continue program being debugged but run?it in reverse

record stop:?停止記錄

2.?格式化（pretty print）打印結構體內容

GDB調試C程序時，默認情況下輸出很不直觀，看起來很費勁.

set print pretty on

3.AddressSanitizerAndDebugger

https://github.com/google/sanitizers/wiki/AddressSanitizerAndDebugger

b __asan::ReportGenericError

p?__asan_describe_address(0x7ffff73c3f80)

4. 條件斷點不生效

設置條件斷點:

cond 1?$rdi==0x0? ?//在斷點一設置條件斷點

b 57 if?$rdi==0x0? ?//在當前文件的57行設置條件斷點

有時候你會發現條件斷點沒有生效，我的解決方案是，先單步運行(n)幾行，在運行c.

Greg 在他的blog中也提到過這個問題：http://www.brendangregg.com/blog/2016-08-09/gdb-example-ncurses.html

5. Command 阻塞

上例中在斷點1設置command,? 先打印堆棧，再continue, 你會發現gdb 還是會被自動阻塞住。

你需要在gdb的配置文件.gdbinit中添加?set height 0，?會自動避免阻塞問題

6.ptype

Print definition of type TYPE. 可以顯示類型的定義。

有個重要參數: \o

/o ? ?? ?print offsets and sizes??of fields in a struct (like pahole)

struct tuv
{
int a1;
char *a2;
int a3;
};

(gdb) ptype /o struct tuv
/* offset | size */ type = struct tuv {
/* 0 | 4 */ int a1;
/* XXX 4-byte hole */
/* 8 | 8 */ char *a2;
/* 16 | 4 */ int a3;
/* total size (bytes): 24 */
}

Notice the format of the first column of comments. There, you
can find two parts separated by the ‘|’ character: the offset, which
indicates where the field is located inside the struct, in bytes, and
the size of the field. Another interesting line is the marker of a hole
in the struct, indicating that it may be possible to pack the struct
and make it use less space by reorganizing its fields.

7 File filename

修改code后，重新build。

gdb無須退出，在gdb中運行 file a.out?命令，新編譯的a.out會自動加載到gdb。

8.?調試多線程

info threads

thread 1

set scheduler-locking on/off/step

set?schedule-multiple on/off

thead apply all bt

thead apply 1 bt

總結

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