我有个很有趣的问题。
我想使用PCRE2和它的JIT函数。任务很简单：从文件中读取行并找到模式。
下面是示例代码：

#include <stdio.h>
#include <string.h>

#define PCRE2_CODE_UNIT_WIDTH 8
#include <pcre2.h>

int search(pcre2_code *re, unsigned char * subject) {

    pcre2_match_data *match_data_real = pcre2_match_data_create_from_pattern(re, NULL);

    size_t len_subject = strlen((const char *)subject);

    int rc = pcre2_match(
        re,
        (PCRE2_SPTR)subject,
        len_subject,
        0,
        0,
        match_data_real,
        NULL
    );

    pcre2_match_data_free(match_data_real);
    return rc;
}

int main(int argc, char ** argv) {

    unsigned char subject[][100]     = {
        "this is a foobar",
        "this is a barfoo",
        "this is a barbar",
        "this is a foofoo"
    };

    pcre2_code *re;
    PCRE2_SPTR  pattern = (unsigned char *)"foo";
    int         errornumber;
    PCRE2_SIZE  erroroffset;

    re = pcre2_compile(
        pattern,
        PCRE2_ZERO_TERMINATED,
        0,
        &errornumber,
        &erroroffset,
        NULL
    );
    pcre2_jit_compile(re, PCRE2_JIT_COMPLETE);

    FILE *fp;

    int s = 0;
    while(s < 2) {
        search(re, subject[s++]);
    }

    if (argc >= 2) {
        fp = fopen(argv[1], "r");
        if (fp != NULL) {
            char tline[2048];
            while(fgets(tline, 2048, fp) != NULL) {
                search(re, (unsigned char *)tline);
            }
            fclose(fp);
        }
    }

    pcre2_code_free(re);

    return 0;
}

编译代码：

gcc -Wall -O2 -g pcretest.c -o pcretest -lpcre2-8

如您所见，在第58行中，我检查了是否有给定的参数，代码尝试将其作为文件打开。
另外，如第49行所示，我希望使用PCRE2的JIT。
这段代码也能正常工作，但我用Valgrind检查了一下，发现了一个有趣的行为：

• 如果我添加一个文件作为参数，那么Valgrind报告Conditional jump or move depends on uninitialised value(s)和Uninitialised value was created by a stack allocation，但是它指向main()。valgrind --tool=memcheck --leak-check=full --show-leak-kinds=all --track-origins=yes -s ./pcretest myfile.txt
• 没有参数，就没有任何Valgrind报告。命令：valgrind --tool=memcheck --leak-check=full --show-leak-kinds=all --track-origins=yes -s ./pcretest
• 如果我在第55行注解掉pcre2_jit_compile((*re), PCRE2_JIT_COMPLETE);，那么一切都正常，没有任何Valgrind报告。命令：valgrind --tool=memcheck --leak-check=full --show-leak-kinds=all --track-origins=yes -s ./pcretest myfile.txt

Valgrind的相关输出：

==31385== Conditional jump or move depends on uninitialised value(s)
==31385==    at 0x4EECD1A: ???
==31385==    by 0x1FFEFFFC1F: ???
==31385==  Uninitialised value was created by a stack allocation
==31385==    at 0x1090FA: main (pcretest.c:27)
...
==31385== HEAP SUMMARY:
==31385==     in use at exit: 0 bytes in 0 blocks
==31385==   total heap usage: 12 allocs, 12 frees, 13,486 bytes allocated
==31385== 
==31385== All heap blocks were freed -- no leaks are possible
==31385== 
==31385== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
==31385== 
==31385== 1 errors in context 1 of 1:
==31385== Conditional jump or move depends on uninitialised value(s)
==31385==    at 0x4EECD1A: ???
==31385==    by 0x1FFEFFFC1F: ???
==31385==  Uninitialised value was created by a stack allocation
==31385==    at 0x1090FA: main (pcretest.c:27)
==31385== 
==31385== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

第27行是int main(...)。
我错过了什么？