gdb：当前上下文中没有符号“郁金香”

Question

我正在尝试编译我的程序并使其可执行，但每次我尝试打印时都说：“当前上下文中没有符号”郁金香“。 “

这是我的代码：

#include <stdlib.h>
#include <stdio.h>

int main() {
unsigned long *daffodil = (unsigned long *) malloc(sizeof(unsigned long));
if (daffodil == (unsigned long *) NULL)
exit(EXIT_FAILURE);
*daffodil = 170;
unsigned long *tulip = daffodil;
unsigned long *carnation = (unsigned long *) malloc(sizeof(unsigned long));
if (carnation == (unsigned long *) NULL)
exit(EXIT_FAILURE);
*carnation = 995;
unsigned long *lily = tulip;
unsigned long crocus = 953;
unsigned long *zinnia = &crocus;
(void) printf("Registering daffodil: %lu.\n", *daffodil);
(void) printf("Registering tulip: %lu.\n", *tulip);
(void) printf("Registering carnation: %lu.\n",*carnation);
(void) printf("Registering lily: %lu.\n", *lily);
(void) printf("Registering crocus: %lu.\n", crocus);
(void) printf("Registering zinnia: %lu.\n", *zinnia);
carnation = (unsigned long *) NULL;
free(daffodil);
free(carnation);

return EXIT_SUCCESS;
}

这是我在终端中所做的事情：

Answer 1

为了在GDB中查看局部变量，你必须打破该函数内的程序执行。您试图在程序终止后打印该值，这是不可能的。

尝试在第10行设置一个断点，我想：

FORMULA1- COLL_DATE
if Collection_Rejection_Desc = 'Cleared'
then Coll_Rej_Dt
else null

FORMULA2- REJ_DATE
if Collection_Rejection_Desc = 'Rejected'
then Coll_Rej_Dt
else null

您也可以在(gdb) br 10 (gdb) run (gdb) print tulip 的开头处中断，然后前进直到变量初始化为止：

main

(gdb) br main (gdb) run (gdb) next (gdb) next (gdb) ... (gdb) print tulip 处的断点非常频繁，main有一个自动执行此操作的命令：gdb。

如果您对变量特别感兴趣，那么您可以显示它，以便在每一步都自动打印：

start