从标准输入获取输入的问题 - 从 valgrind 读取/写入无效答案

【问题标题】：Problems with taking input from stdin - Invalid read/write from valgrind从标准输入获取输入的问题 - 从 valgrind 读取/写入无效
【发布时间】：2015-02-12 01:05:19
【问题描述】：

我在我正在处理的程序上运行了 valgrind，但出现以下错误 - 我不知道为什么。任何帮助将不胜感激。如果您需要更多信息，请告诉我

==27928== Invalid read of size 1
==27928==    at 0x4EB9390: __GI___rawmemchr (rawmemchr.S:25)
==27928==    by 0x4EA514F: _IO_str_init_static_internal (strops.c:45)
==27928==    by 0x4E86D64: __isoc99_vsscanf (isoc99_vsscanf.c:42)
==27928==    by 0x4E86CF7: __isoc99_sscanf (isoc99_sscanf.c:33)
==27928==    by 0x401A76: countAndSort (lab1.c:442)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==  Address 0x55bb040 is 0 bytes inside a block of size 10,000,000 free'd
==27928==    at 0x4C27D4E: free (vg_replace_malloc.c:427)
==27928==    by 0x4019D6: countAndSort (lab1.c:430)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==
==27928== Invalid read of size 1
==27928==    at 0x4C2B834: __GI___rawmemchr (mc_replace_strmem.c:1110)
==27928==    by 0x4EA514F: _IO_str_init_static_internal (strops.c:45)
==27928==    by 0x4E86D64: __isoc99_vsscanf (isoc99_vsscanf.c:42)
==27928==    by 0x4E86CF7: __isoc99_sscanf (isoc99_sscanf.c:33)
==27928==    by 0x401A76: countAndSort (lab1.c:442)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==  Address 0x55bb041 is 1 bytes inside a block of size 10,000,000 free'd
==27928==    at 0x4C27D4E: free (vg_replace_malloc.c:427)
==27928==    by 0x4019D6: countAndSort (lab1.c:430)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==
==27928== Invalid read of size 1
==27928==    at 0x4E7D920: _IO_vfscanf (vfscanf.c:620)
==27928==    by 0x4E86D79: __isoc99_vsscanf (isoc99_vsscanf.c:44)
==27928==    by 0x4E86CF7: __isoc99_sscanf (isoc99_sscanf.c:33)
==27928==    by 0x401A76: countAndSort (lab1.c:442)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==  Address 0x55bb040 is 0 bytes inside a block of size 10,000,000 free'd
==27928==    at 0x4C27D4E: free (vg_replace_malloc.c:427)
==27928==    by 0x4019D6: countAndSort (lab1.c:430)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==
==27928== Invalid read of size 1
==27928==    at 0x4EA36D2: _IO_sputbackc (genops.c:731)
==27928==    by 0x4E7D97B: _IO_vfscanf (vfscanf.c:625)
==27928==    by 0x4E86D79: __isoc99_vsscanf (isoc99_vsscanf.c:44)
==27928==    by 0x4E86CF7: __isoc99_sscanf (isoc99_sscanf.c:33)
==27928==    by 0x401A76: countAndSort (lab1.c:442)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==  Address 0x55bb040 is 0 bytes inside a block of size 10,000,000 free'd
==27928==    at 0x4C27D4E: free (vg_replace_malloc.c:427)
==27928==    by 0x4019D6: countAndSort (lab1.c:430)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==
==27928== Invalid read of size 1
==27928==    at 0x4E7DC7D: _IO_vfscanf (vfscanf.c:1394)
==27928==    by 0x4E86D79: __isoc99_vsscanf (isoc99_vsscanf.c:44)
==27928==    by 0x4E86CF7: __isoc99_sscanf (isoc99_sscanf.c:33)
==27928==    by 0x401A76: countAndSort (lab1.c:442)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==  Address 0x55bb040 is 0 bytes inside a block of size 10,000,000 free'd
==27928==    at 0x4C27D4E: free (vg_replace_malloc.c:427)
==27928==    by 0x4019D6: countAndSort (lab1.c:430)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==
==27928== Invalid read of size 1
==27928==    at 0x4E7E9EF: _IO_vfscanf (vfscanf.c:1781)
==27928==    by 0x4E86D79: __isoc99_vsscanf (isoc99_vsscanf.c:44)
==27928==    by 0x4E86CF7: __isoc99_sscanf (isoc99_sscanf.c:33)
==27928==    by 0x401A76: countAndSort (lab1.c:442)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==  Address 0x55bb041 is 1 bytes inside a block of size 10,000,000 free'd
==27928==    at 0x4C27D4E: free (vg_replace_malloc.c:427)
==27928==    by 0x4019D6: countAndSort (lab1.c:430)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==
==27928== Invalid read of size 1
==27928==    at 0x4EA36D2: _IO_sputbackc (genops.c:731)
==27928==    by 0x4E7DDF3: _IO_vfscanf (vfscanf.c:1811)
==27928==    by 0x4E86D79: __isoc99_vsscanf (isoc99_vsscanf.c:44)
==27928==    by 0x4E86CF7: __isoc99_sscanf (isoc99_sscanf.c:33)
==27928==    by 0x401A76: countAndSort (lab1.c:442)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==  Address 0x55bb041 is 1 bytes inside a block of size 10,000,000 free'd
==27928==    at 0x4C27D4E: free (vg_replace_malloc.c:427)
==27928==    by 0x4019D6: countAndSort (lab1.c:430)
==27928==    by 0x4014EB: doProcess (lab1.c:316)
==27928==    by 0x4011C2: main (lab1.c:211)
==27928==

无论您从每个错误的根源如何想，通过大量的试验和错误，在代码块中注释掉/返回以及在测试编译中单独测试代码片段，我发现以下是错误的来源。如果我在程序中注释掉这段代码，所有错误都会消失。

注意：整数是全局 int* 类型。 countToUse 是一个全局 int 类型。此处代码的目标是从标准输入读取所有整数并将它们放入正确大小的动态数组中。

            // Load stdin into a buffer
            char *buffer = malloc(BUFFER_SIZE);
            if(buffer == NULL){
                    fprintf(stderr, "Malloc for stdin buffer in countAndSort() failed. Exiting.\n");
                    exit(1);
            }
            if (fgets(buffer, BUFFER_SIZE, stdin) == NULL) {
                    fprintf(stderr, "Error loading input from stdin into buffer. Exiting.\n");
                    exit(1);
            }

            // Get a count of the numbers to create the array
            int count = 0;
            int index = 0;
            int num, delta;
            while (index < BUFFER_SIZE && sscanf(&buffer[index], "%d%n", &num, &delta) == 1){
                    count++;
                    index += delta;
            }

            // Initialize the array with the proper size
            integers = malloc(count*sizeof(int));
            if(integers == NULL){
                    fprintf(stderr, "Malloc for integer array in countAndSort() failed. Exiting. \n");
                    exit(1);
            }

            // Load the integers into the array
            index = 0;
            for (int i = 0; i < count; i++){
// LINE 442 IS RIGHT BELOW THIS LINE ------------------------------------
                    if (index < BUFFER_SIZE && sscanf(&buffer[index], "%d%n", &integers[i], &delta) != 1){
                            fprintf(stderr, "There was a problem reading the buffer!\n");
                            exit(1);
                    }
                    index += delta;
            }

            if(buffer != NULL)
                    free(buffer);

            countToUse = count;

【问题讨论】：

doProcess()在哪里
@Cyclone 不是doProcess引起的。我已经排除了。 doProcess（在第 323 行）调用包含此代码的函数（countAndSort）。
@Cyclone 第 323 行在计数过程中读取“countAndSort()”
这太大了char buffer[10000000];，你可以malloc() 它溢出堆栈。堆栈有一个限制，我认为是8388608，尝试使用ulimit -s 并将该数字乘以1024。
你在此行上方释放 buffer10 行

标签： c io stdin fgets scanf

【解决方案1】：

你需要确保你没有超出buffer的范围，像这样

while ((index < 10000000) && (sscanf(&buffer[index], "%d%n", &num, &delta) == 1))

这同样适用于所有buffer[index]。

另外，从错误来看，您似乎拥有free()d buffer，然后尝试从中读取。

【讨论】：

我进行了这些更改，但仍然存在相同的错误