4行目のprocess_query_strで、splitlineを呼び出し、3つの要素の文字列配列を取得します。最後の要素はNULLです。配列はmallocされており、個々の文字列も同様です。次に、各要素を解放してから、配列自体を解放しようとします（最初の関数の終わりに向かって）。最初の2つの文字列は解放されますが、3番目の要素（NULL）を解放すると、無効なポインターに関するエラーが下部に表示されます。どうやらそれはNULLに設定されていないので、そうする必要があります。ブレークポイントを設定しようとしましたが、プログラムが停止しません。
char * process_query_str(char *rq, char *cmd) {
logg("In process_query_str.\n");
int has_query = 0;
char **tokenized_args = splitline(rq, &has_query); //Tokenize the string based on '?'
char * query_str = rq;
logg("has_query:");
fprintf(stderr, "%d", has_query);
if (has_query == 1) //Check for Query String
if (query_str != NULL) {
query_str = retrieve_query_str(tokenized_args);
logg("Query String: ");
logg(query_str);
logg("\n");
char* key = "REQUEST_METHOD"; //Process REQUEST_METHOD envir variable
if (VLstore(key, cmd) == 0)
if (VLexport(key) == 0) {
logg("Successfully exported ");
logg(cmd);
logg(": ");
logg(key);
logg("\n");
key = "QUERY_STRING"; //Process QUERY_STRING envir variable
if (VLstore(key, query_str) != 1) //1 signals a problem
if (VLexport(key) != 0) //0 signals a problem
{
logg("Successfully exported ");
logg(cmd);
logg(": ");
logg(key);
logg("\n");
}
}
}
#ifdef LOGGING //Print out environment variables
VLlist();
#endif
char *resource_str = newstr(tokenized_args[0], strlen(tokenized_args[0]));
freelist(tokenized_args);
logg("resource_str=");
logg(resource_str);
logg("\n");
return resource_str;
}
char ** splitline(char *line, int*has_query)
/*
* purpose: split a line into array of white-space separated tokens
* returns: a NULL-terminated array of pointers to copies of the tokens
* or NULL if line if no tokens on the line
* action: traverse the array, locate strings, make copies
* note: strtok() could work, but we may want to add quotes later
*/
{
//char *newstr();
logg("In splitline\n");
char **args;
int spots = 0; /* spots in table */
int bufspace = 0; /* bytes in table */
int argnum = 0; /* slots used */
char *cp = line; /* pos in string */
char *start;
int len;
if (line == NULL) /* handle special case */
return NULL;
args = emalloc(BUFSIZ); /* initialize array */
bufspace = BUFSIZ;
spots = BUFSIZ / sizeof(char *);
while (*cp != '\0') {
logg("*cp=");
fprintf(stderr, "%c", *cp);
while (*cp == ' ') /* skip leading spaces */
cp++;
if (*cp == '\0') /* quit at end-o-string */
break;
/* make sure the array has room (+1 for NULL) */
if (argnum + 1 >= spots) {
args = erealloc(args, bufspace + BUFSIZ);
bufspace += BUFSIZ;
spots += (BUFSIZ / sizeof(char *));
}
/* mark start, then find end of word */
start = cp;
len = 1;
if (*cp == '?') {
logg("query reached.\n");
*has_query = 1;
}
while (*++cp != '\0' && !(is_delim(*cp,*has_query)))
len++;
args[argnum++] = newstr(start, len);
}
logg("arg[0] =");
logg(args[0]);
logg("\n");
if (argnum == 2) {
logg("arg[1] =");
logg(args[1]);
logg("\n");
}
args[argnum] = NULL;
fprintf(stderr, "last element is NULL. argnum=%d", argnum);
return args;
}
void freelist(char **list)
/*
* purpose: free the list returned by splitline
* returns: nothing
* action: free all strings in list and then free the list
*/
{
char **cp = list;
while (*cp && (*cp)) {
logg("free: ");logg(*cp);logg("\n");
free(*cp++);
}
logg("Now Free the list:");logg("\n");
free(list);
logg("Done Freeing List\n");
}
から取得するスタックバックトレース情報glibcは次のとおりです。
free: /index.cgifree: key=value*** glibc detected *** ./ws: free(): invalid pointer: 0x0804efa9 ***
======= Backtrace: =========
/lib/tls/i686/cmov/libc.so.6[0xb76d3d05]
/lib/tls/i686/cmov/libc.so.6(cfree+0x90)[0xb76d7770]
./ws[0x804b36f]
./ws[0x804a1fb]
./ws[0x8049de1]
./ws[0x8049757]
./ws[0x8049660]
/lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xe0)[0xb767e460]
./ws[0x8049031]
======= Memory map: ========
08048000-0804d000 r-xp 00000000 00:24 8084895 /nfs/home/j/c/jcalderon/unixlin ux/wsng/ws
0804d000-0804e000 rw-p 00004000 00:24 8084895 /nfs/home/j/c/jcalderon/unixlin ux/wsng/ws
0804e000-0806f000 rw-p 0804e000 00:00 0 [heap]
b7500000-b7521000 rw-p b7500000 00:00 0
b7521000-b7600000 ---p b7521000 00:00 0
b7644000-b764e000 r-xp 00000000 68:07 1122448 /lib/libgcc_s.so.1
b764e000-b764f000 rw-p 0000a000 68:07 1122448 /lib/libgcc_s.so.1
b765c000-b7665000 r-xp 00000000 68:07 1122335 /lib/tls/i686/cmov/libnss_files -2.7.so
b7665000-b7667000 rw-p 00008000 68:07 1122335 /lib/tls/i686/cmov/libnss_files -2.7.so
b7667000-b7668000 rw-p b7667000 00:00 0
b7668000-b77b2000 r-xp 00000000 68:07 1122611 /lib/tls/i686/cmov/libc-2.7.so
b77b2000-b77b3000 r--p 0014a000 68:07 1122611 /lib/tls/i686/cmov/libc-2.7.so
b77b3000-b77b5000 rw-p 0014b000 68:07 1122611 /lib/tls/i686/cmov/libc-2.7.so
b77b5000-b77b8000 rw-p b77b5000 00:00 0
b77c2000-b77c7000 rw-p b77c2000 00:00 0
b77c7000-b77c8000 r-xp b77c7000 00:00 0 [vdso]
b77c8000-b77e2000 r-xp 00000000 68:07 1124008 /lib/ld-2.7.so
b77e2000-b77e4000 rw-p 00019000 68:07 1124008 /lib/ld-2.7.so
bfd9f000-bfdb4000 rw-p bffea000 00:00 0 [stack]