什麼時候釋放變量decodeSet1？

Question

我分配內存給decodeSet1和decodeSet2 ...我可以免費decodeSet2罰款，但是當免費decodeSet1並提交我的代碼嘗試給出這個錯誤「雙免費或腐敗（出）：0x0000000002046020 *** ...但是當我在Valgrind的運行代碼也沒有給我erors ...

這裏是我的代碼：

#define __STDC_FORMAT_MACROS 
#include <inttypes.h> 
#include <stdlib.h> 
#include <stdio.h> // size_t type 
#include <string.h> // C strings 
#include <stdint.h> // uint64_t type 

#define NUL '\0' 
const size_t SETSIZE = sizeof(uint64_t) << 3 ; 
const size_t BUFSIZE = 256; 
const char encodingTable[] = {'z', 'y', 'x', 'w', 'v', 'u', 't', 's', 
           'r', 'q', 'p', 'o', 'n', 'm', 'l', 'k', 
           'j', 'i', 'h', 'g', 'f', 'e', 'd', 'c', 
           'b', 'a', ',', '9', '8', '7', '6', '5', 
           '4', '3', '2', '1', '0', '.', 'Z', 'Y', 
           'X', 'W', 'V', 'U', 'T', 'S', 'R', 'Q', 
           'P', 'O', 'N', 'M', 'L', 'K', 'J', 'I', 
           'H', 'G', 'F', 'E', 'D', 'C', 'B', 'A'}; 


// Encodes a string 
// 
// @param st a string to be encoded 
uint64_t set_encode(char * st) { 
    unsigned long long bitMask = 1; 
    uint64_t set = 0; 
    for(size_t x = 0; x < strlen(st); x ++){ 
     int indx = strchr(encodingTable, st[x]) - encodingTable; 
     if(indx >= 0){ 
      set |= bitMask << indx; 
     } 
    } 
    return set; 
} 

// The intersection of two sets 
// 
// @param set1 a set of characters from files or a string 
// @param set2 a set of characters from files or a string 
uint64_t set_intersect(uint64_t set1, uint64_t set2) { 
    uint64_t set = 0; 
    set = set1 & set2; 
    return set; 
} 

// The union of two sets 
// 
// @param set1 a set of characters from files or a string 
// @param set2 a set of characters from files or a string 
uint64_t set_union(uint64_t set1, uint64_t set2) { 
    uint64_t set = 0; 
    set = set1 | set2; 
    return set; 
} 

// The complement of a set 
// 
// @param set1 a set of characters from files or a string 
uint64_t set_complement(uint64_t set1) { 
    uint64_t set = 0; 
    set = ~set1; 
    return set; 
} 

// Takes the difference of set1 and ~set2 
// 
// @param set1 a set of characters from files or a string 
// @param set2 a set of characters from files or a string 
uint64_t set_difference(uint64_t set1, uint64_t set2) { 
    uint64_t set = 0; 
    set = set1 & ~set2; 
    return set; 
} 

// Takes the difference of the union of set1 and set2 and 
// the intersect of set1 and set2. 
// 
// @param set1 a set of characters from files or a string 
// @param set2 a set of characters from files or a string 
uint64_t set_symdifference(uint64_t set1, uint64_t set2) { 
    uint64_t set = 0; 
    set = set_union(set1, set2) - set_intersect(set1, set2); 
    return set; 
} 

// Takes the cardinality of a set (number of 1's in its binary 
// number. 
// 
// @param set a set of characters from files or a string 
size_t set_cardinality(uint64_t set) { 
    size_t cnt = 0; 
    for (size_t x = 0; x < SETSIZE; x++){ 
     set >>= 1UL; 
     if (set & 1){ 
      cnt++; 
     } 
    } 
    return cnt; 
} 

// Decodes a set 
// 
// @param set a set of characters from files or a string 
char * set_decode(uint64_t set) { 
    size_t lengthOfSet = set_cardinality(set); 
    size_t indx = 0; 
    char *bits = malloc(lengthOfSet + 1); 
    bits[lengthOfSet] = NUL; 

    for (size_t cnt = 0; set; set >>= 1){ 
     if (set & 1){ 
      bits[lengthOfSet - indx - 1] = encodingTable[cnt]; 
      indx += 1; 
     } 
     cnt += 1; 
    } 
    return bits; 
} 

// Reads a string from a file and encodes it 
// 
// @param fp file to be read 
uint64_t file_set_encode(FILE * fp) { 
    char buf[BUFSIZE]; 
    uint64_t set = 0; 

    while (fgets(buf, BUFSIZ, fp) != NULL){ 
     uint64_t tmpBuf = set_encode(buf); 
     set |= tmpBuf; 
    } 
    fclose(fp); 
    return set; 
} 

int main(int argc, char *argv[]){ 
    int args; 
    uint64_t set1 = 0; 
    uint64_t set2 = 0; 
    args = argc - 1; 
    char *decodeSet1 = NULL; 
    char *decodeSet2 = NULL; 

    if (args < 2 || args > 2){ 
     fprintf(stderr, "Usage: file-bitsets string1 string2"); 
     exit(EXIT_FAILURE); 
    } else { 
     FILE *pfile1 = fopen(argv[1], "r"); 
     if (pfile1){ 
      set1 = file_set_encode(pfile1); 
      printf("string1:  %s\tEncoding the file: %s\n", argv[1], argv[1]); 
     } else { 
      set1 = set_encode(argv[1]); 
      printf("string1:  %s\tEncoding the string: %s\n", argv[1], argv[1]); 
     } 

     FILE *pfile2 = fopen(argv[2], "r"); 
     if (pfile2){ 
      set2 = file_set_encode(pfile2); 
      printf("string2:  %s\tEncoding the file: %s\n\n", argv[2], argv[2]); 
     } else { 
      set2 = set_encode(argv[2]); 
      printf("string2:  %s\tEncoding the string: %s\n\n", argv[2], argv[2]); 
     } 

     printf("set1: %#018lx\n", set1); 
     printf("set2: %#018lx\n\n", set2); 

     printf("set_intersect: %#018lx\n", set_intersect(set1, set2)); 
     printf("set_union: %#018lx\n\n", set_union(set1, set2)); 

     printf("set1 set_complement: %#018lx\n", set_complement(set1)); 
     printf("set2 set_complement: %#018lx\n\n", set_complement(set2)); 

     printf("set_difference:  %#018lx\n", set_difference(set1, set2)); 
     printf("set_symdifference: %#018lx\n\n", set_symdifference(set1, set2)); 

     printf("set1 set_cardinality: %zu\n", set_cardinality(set1)); 
     printf("set2 set_cardinality: %zu\n\n", set_cardinality(set2)); 

     decodeSet1 = set_decode(set1); 
     decodeSet2 = set_decode(set2); 
     printf("members of set1: '%s'\n", decodeSet1); 
     printf("members of set2: '%s'\n", decodeSet2); 
    } 
-> free(decodeSet1); 
    free(decodeSet2); 
} 

這裏是我得到的錯誤，當我提交嘗試服務器：

SaholinGOD@comp:~/Desktop/$ try grd-243 hw7-1 file-bitsets.c 
Copying files...done 
Initializing - please wait... 
ON-TIME submission of hw7-1 
Compiling your submission.... 
gcc -ggdb -std=c99 -Wall -Wextra -pedantic -c file-bitsets.c 
gcc -ggdb -std=c99 -Wall -Wextra -pedantic -o file-bitsets file-bitsets.o -lm 
Test 1: file-bitsets Hello There < input.1 
Test 2: file-bitsets chimchiminy chimchimeny < input.2 
Test 3: file-bitsets empty aMixedBag < input.3 
Still testing... 
*** Error in `file-bitsets': double free or corruption (out): 0x0000000002046020 *** 
======= Backtrace: ========= 
/lib/x86_64-linux-gnu/libc.so.6(+0x77725)[0x2ac1765d1725] 
/lib/x86_64-linux-gnu/libc.so.6(+0x7ff4a)[0x2ac1765d9f4a] 
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x2ac1765ddabc] 
file-bitsets[0x400ec2] 
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x2ac17657a830] 
file-bitsets[0x400789] 
======= Memory map: ======== 
00400000-00402000 r-xp 00000000 00:42 24942233       /home/grader/grd-243/try_dir/Wds/wd.ShaolinGOD/file-bitsets 
00601000-00602000 r--p 00001000 00:42 24942233       /home/grader/grd-243/try_dir/Wds/wd.ShaolinGOD/file-bitsets 
00602000-00603000 rw-p 00002000 00:42 24942233       /home/grader/grd-243/try_dir/Wds/wd.ShaolinGOD/file-bitsets 
02026000-02047000 rw-p 00000000 00:00 0         [heap] 
2ac176332000-2ac176358000 r-xp 00000000 08:01 7042504     /lib/x86_64-linux-gnu/ld-2.23.so 
2ac176358000-2ac17635b000 rw-p 00000000 00:00 0 
2ac17639f000-2ac1763a1000 rw-p 00000000 00:00 0 
2ac176557000-2ac176558000 r--p 00025000 08:01 7042504     /lib/x86_64-linux-gnu/ld-2.23.so 
2ac176558000-2ac176559000 rw-p 00026000 08:01 7042504     /lib/x86_64-linux-gnu/ld-2.23.so 
2ac176559000-2ac17655a000 rw-p 00000000 00:00 0 
2ac17655a000-2ac17671a000 r-xp 00000000 08:01 7042508     /lib/x86_64-linux-gnu/libc-2.23.so 
2ac17671a000-2ac176919000 ---p 001c0000 08:01 7042508     /lib/x86_64-linux-gnu/libc-2.23.so 
2ac176919000-2ac17691d000 r--p 001bf000 08:01 7042508     /lib/x86_64-linux-gnu/libc-2.23.so 
2ac17691d000-2ac17691f000 rw-p 001c3000 08:01 7042508     /lib/x86_64-linux-gnu/libc-2.23.so 
2ac17691f000-2ac176923000 rw-p 00000000 00:00 0 
2ac176923000-2ac176939000 r-xp 00000000 08:01 7042529     /lib/x86_64-linux-gnu/libgcc_s.so.1 
2ac176939000-2ac176b38000 ---p 00016000 08:01 7042529     /lib/x86_64-linux-gnu/libgcc_s.so.1 
2ac176b38000-2ac176b39000 rw-p 00015000 08:01 7042529     /lib/x86_64-linux-gnu/libgcc_s.so.1 
2ac178000000-2ac178021000 rw-p 00000000 00:00 0 
2ac178021000-2ac17c000000 ---p 00000000 00:00 0 
7ffe33980000-7ffe339a1000 rw-p 00000000 00:00 0       [stack] 
7ffe339ce000-7ffe339d0000 r--p 00000000 00:00 0       [vvar] 
7ffe339d0000-7ffe339d2000 r-xp 00000000 00:00 0       [vdso] 
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0     [vsyscall] 
Still testing... 
Test 10: file-bitsets < input.10 

Creating submission archive - please wait.... 
Files being saved: 
file-bitsets.c 


Submission dated 2016/11/17 19:31:28 has been completed 
Your files: file-bitsets.c 

Answer 1

有一個微妙的錯誤，你可以通過電話看到set_decode(1)。 set_cardinality(1)將返回0，因爲set >>= 1UL發生在檢查之前，看看set & 1是否爲真。

然後，您char *bits = malloc(1);依次爲：

if (1 & 1){ 
    bits[0 - 0 - 1] = encodingTable[cnt]; 

哎呀，寫bits[-1]腐敗堆，讓您看到錯誤。修正得到set_cardinality返回奇數的正確值應該是顯而易見的，所以我會讓你去做。