我为decodeSet1和decodeSet2分配了内存...我可以免费解码decodeSet2，但是当免费使用decodeSet1并提交我的代码尝试它时会出现此错误＆＃34; double free或corruption（out）：0x0000000002046020 ** * ...但是当我在valgrind中运行代码时，它没有给我任何错误......
这是我的代码：
#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);
}
这是我提交给try服务器时遇到的错误：
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
答案 0 :(得分：1)
有一个微妙的错误，您可以通过调用set_decode(1)来查看。 set_cardinality(1)会在检查前0返回set >>= 1UL，以查看set & 1是否为真。
然后，您char *bits = malloc(1);后跟：
if (1 & 1){
bits[0 - 0 - 1] = encodingTable[cnt];
哎呀，写bits[-1]会破坏堆，给你看错。让set_cardinality为奇数返回正确值的修复应该是显而易见的，所以我会留下让你这样做。