CUPS打印文件分割故障

Question

我在试着制作一个杯子打印系统。我想得到打印机的状态，到目前为止打印了多少页等等。

为此，我正在执行CUPS示例中给出的示例程序。

#include <cups/cups.h>
#include <stdio.h>


int main(){

int num_options;
cups_option_t *options;

cups_dest_t *dests;
int num_dests = cupsGetDests(&dests);
cups_dest_t *dest = cupsGetDest("name", NULL, num_dests, dests);
int job_id;

/* Print a single file */
job_id = cupsPrintFile(dest->name, "testfile.txt", "Test Print", num_options, options);

cupsFreeDests(num_dests, dests);

return 0;
}

我使用gcc myfile.c -o myout -lcups编译它

当我尝试执行./myout时

我得到了

分段故障

我使用树莓-π3板作为我的CUPS服务器。

提前谢谢。

Answer 1

dest指向无效地址.

cups_dest_t *dest; // declared but not initialized or assigned afterwards 

所以去引用它(cupsPrintFile(dest->name.)是UB，可以导致SegFault。

这是您应该如何使用它(摘自这里)：

#include <cups/cups.h>

cups_dest_t *dests;
int num_dests = cupsGetDests(&dests);
cups_dest_t *dest = cupsGetDest("name", NULL, num_dests, dests);

/* do something with dest */

cupsFreeDests(num_dests, dests);

更新：

您的代码不处理某些变量(即不初始化-坏)。我看到的第一个是cups_option_t *options;。照顾好所有的变量，如果不起作用的话-调试。

int main(){

int num_options;
cups_option_t *options; // add a call to "cupsAddOption("first", "value", num_options, &options);"

cups_dest_t *dests;
int num_dests = cupsGetDests(&dests);
cups_dest_t *dest = cupsGetDest("name", NULL, num_dests, dests);
int job_id;

/* Print a single file */
job_id = cupsPrintFile(dest->name, "testfile.txt", "Test Print", num_options, options); // options is used here but is uninitialized

cupsFreeDests(num_dests, dests);

return 0;
}