我正在嘗試查找新程式中發生損壞的位置/時間。程式只有495行，gdb沒有幫我除錯。（至少，不是我目前的知識集。）考慮以下幾點：
> gdb psgrep-2020
(comments omitted)
Reading symbols from psgrep-2020...
(gdb) b 466
Breakpoint 1 at 0x3073: file psgrep-2020.c, line 466.
(gdb) run -F dnsmasq
Starting program: /usr/local/src/psgrep-2022/psgrep-2020 -F dnsmasq
Breakpoint 1, showProcess (pid=893) at psgrep-2020.c:466
466 if (printCmdline) {
(gdb) step
467 procNameFromCmdline(pid, strWork, sizeof(strWork), TRUE) ;
(gdb) p pid
$1 = 893
(gdb) p strWork
$2 = '\000' <repeats 1023 times>
(gdb) print sizeof(strWork)
$3 = 1024
(gdb) step
procNameFromCmdline (pid=0, result=0x0, resultLen=0, fullCmd=0 '\000') at psgrep-2020.c:58
58 int procNameFromCmdline(pid_t pid, char *result, int resultLen, BOOL fullCmd) {
(gdb)
在被呼叫行程（procNameFromCmdline）開始時，我們可以看到每個引數都不正確（通過#define TRUE 等于 1）。有時 gdb 顯示如下：
procNameFromCmdline (pid=0, result=0x19c5b4 <error: Cannot access memory at address 0x19c5b4>, resultLen=1689012, fullCmd=0 '\000')
我不是想讓其他人為我找到問題；我想做的是找到一種方法來檢測程式何時損壞。我相信我所有的 memset、snprintf() 等都得到了正確的約束；很明顯，雖然有些事情出了差錯。
如果有任何幫助并正確看待事情，這里是呼叫之前的周圍代碼......
fpProcFile = fopen(sProcPath, "rt") ; // Open the stat file for reading text
if (fpProcFile) {
fscanf(fpProcFile
, "%d %s %c %d %d %d %d %d %u %lu %lu %lu %lu %lu %lu %ld %ld %ld %ld %ld "
"%ld %llu %lu %ld %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %d %d %u "
"%u %llu %lu %ld %lu %lu %lu %lu %lu %lu %lu %d"
, &(s->pid), s->comm, &(s->state), &(s->ppid), &(s->pgrp)
, &(s->session), &(s->tty_nr), &(s->tpgid), &(s->flags), &(s->minflt)
, &(s->cminflt), &(s->majflt), &(s->cmajflt), &(s->utime), &(s->stime)
, &(s->cutime), &(s->cstime), &(s->priority), &(s->nice), &(s->num_threads)
, &(s->itrealvalue), &(s->starttime), &(s->vsize), &(s->rss), &(s->rsslim)
, &(s->startcode), &(s->endcode), &(s->startstack), &(s->kstkesp), &(s->kstkeip)
, &(s->signal), &(s->blocked), &(s->sigignore), &(s->sigcatch), &(s->wchan)
, &(s->nswap), &(s->cnswap), &(s->exit_signal), &(s->processor), &(s->rt_priority)
, &(s->policy), &(s->delayacct_blkio_ticks)
, &(s->guest_time), &(s->cguest_time), &(s->start_data)
, &(s->end_data), &(s->start_brk), &(s->arg_start), &(s->arg_end), &(s->env_start)
, &(s->env_end), &(s->exit_code)
) ;
fclose(fpProcFile) ;
processName = s->comm ;
memset(strWork, 0x00, sizeof(strWork)) ;
if (printCmdline) {
procNameFromCmdline(pid, strWork, sizeof(strWork), TRUE) ;
（該 fscanf 中唯一的 %s 指向一個 char[65535] 并且 /fproc/893/stat 中該欄位的值的長度為 9 加上一個終止符。根據檔案，16 就足夠了。但這不是重點。 )
有辦法嗎？我需要更專業的除錯器嗎？
（雖然我不是在找人來解決這個程式的問題，但似乎引起了一些興趣。鑒于此，我發布了參考代碼中使用的結構。）這記錄在 linux 內核源代碼（fs /proc/array.c) 和（不是我的版本）可以在 [here][1] 和許多其他地方看到。
struct myProcStat {
int pid ; // Process ID
char comm[65535] ; // Command name limited to 16 bytes
char state ; // R=Running S=Sleeping D=WaitingDisk Z=Zombie T=Stopped
// t=TracingStopped W=Paging X=Dead x=Dead K=Wakekill
// W=Waking P=Parked
int ppid ; // Parent process ID
int pgrp ; // Process group ID
int session ; // Session ID
int tty_nr ; // Controlling terminal
int tpgid ; // Foreground process group
unsigned int flags ; // Kernel flags
unsigned long int minflt ; // Number of minor faults
unsigned long int cminflt ; // Children's minor faults
unsigned long int majflt ; // Number of major faults
unsigned long int cmajflt ; // Children's major faults
unsigned long int utime ; // Amount of time scheduled user mode
unsigned long int stime ; // Amount of time scheduled kernel mode
long int cutime ; // Amount of time waited-for children scheduled user mode
long int cstime ; // Amount of time waited-for children scheduled kernel mode
long int priority ; // Priority running real-time scheduling policy
long int nice ; // Nice value
long int num_threads ; // Number of threads in this process
long int itrealvalue ; // Time in jiffies before next SIGALARM is sent
// 21 above, 22 next ...
unsigned long long int starttime ; // Start tine (in clock ticks) after system boot (divide by sysconf(_SC_CLK_TCK))
unsigned long int vsize ; // Virtual memory size in bytes
long int rss ; // Resident set size
unsigned long int rsslim ; // Current soft limit in bytes on rss
unsigned long int startcode ; // address above which text can be run
unsigned long int endcode ; // Address below which text can be run
unsigned long int startstack ; // Address of the start (bottom) of the stack
unsigned long int kstkesp ; // Current stack pointer from kernel perspective
unsigned long int kstkeip ; // Current EIP (instruction pointer)
unsigned long int signal ; // Bitmap of pending signals as a decimal number. Obsolete. use /proc/[pid]/status instead.
unsigned long int blocked ; // Bitmap of blocked signals. Obsolete. Use /proc/[pid]/status instead
unsigned long int sigignore ; // Bitmap of ignored signals. Obsolete, use /proc/[pid]/status instead
unsigned long int sigcatch ; // Bitmap of caught signals. Use /proc/[pid]/status instead
unsigned long int wchan ; // Channel in which process is waiting. Use with /proc/[pid]/wchan
unsigned long int nswap ; // Number of pages swapped (not maintained - ignore)
unsigned long int cnswap ; // Number of child process pages swapped (not maintained - ignore)
int exit_signal ; // Signal to be sent to parent upon death
int processor ; // CPU last executed on
unsigned int rt_priority ; // Real-time scheduling priority
unsigned int policy ; // Scheduling policy for real-time scheduling
unsigned long long int delayacct_blkio_ticks ; // Aggregated block I/O delays, in clock ticks
unsigned long int guest_time ; // Guest time (time spent running virtual CPU for guest OS)
unsigned long int cguest_time ; // Guest time of processes' children
unsigned long int start_data ; // Address above which program BSS data are placed
unsigned long int end_data ; // Address below which program BSS data are placed
unsigned long int start_brk ; // Address above which program heap can be expanded
unsigned long int arg_start ; // Address above which program command-line arguments (argv) are placed
unsigned long int arg_end ; // Address below which argv are placed
unsigned long int env_start ; // Address above which environment is placed
unsigned long int env_end ; // Address below which environment is placed
int exit_code ; // The thread's exit status in form reported by waitpid(2)
} ;
[1]: https://elixir.bootlin.com/linux/latest/source/fs/proc/array.c
uj5u.com熱心網友回復：
在被呼叫行程（procNameFromCmdline）開始時，我們可以看到每個引數都不正確
這很可能意味著 GDB 沒有跳過函式序言（就像它應該的那樣）。很可能是因為這個。
如果你再做一個stepor next，引數會突然再次變得正確。
請注意，上述錯誤已在較新的 GDB 版本中得到修復，因此更新 GDB 是另一種解決方案。
轉載請註明出處，本文鏈接：https://www.uj5u.com/qianduan/430653.html