C语言 瓦尔格林德 条件跳转或移动取决于未初始化的值 mktime() 或浅拷贝问题

Question

浏览了各种来源以寻找解决方案，但找不到问题。我正在尝试将一个字符串（格式化为time_t转换）time_t转换为validate_date（char * date， time_t datefrom， time_t dateto）;。

该错误表明我正在访问一个未初始化的变量，参数 char * date 可以访问（通过打印）并且定位错误，time_t datefrom，dateto 都包含 0。

法典：

void test_print(CalComp * comp_cpy){
    printf("Test print of copy...n");
    for(int i = 0; i < comp_cpy->ncomps; i++){
        printf("Object: (%s)n", comp_cpy->comp[i]->name);
    }
}
/*make a shallow copy of CalComp*/
CalComp * event_copy(CalComp * comp){
    CalComp * cpy = malloc(sizeof(CalComp) + comp->ncomps * sizeof(CalComp*));
    *cpy = *comp;
    memcpy(cpy->comp, comp->comp, comp->ncomps * sizeof(CalComp*));
    return cpy;
}

/*check if date is between datefrom and dateto*/
bool validate_date(char * date, time_t datefrom, time_t dateto){
    struct tm tm;
    char temp[1000], *token;
    strcpy(temp,date);
    token = strtok(temp, "Z");
    if(strptime(token, "%Y%m%dT%H%M%S", &tm)==NULL){ //check if conversion to struct tm is successful
            perror("validate_date converting date error");
            exit(-1);
    }
    time_t tm_date;
    if((tm_date = mktime(&tm)) == -1){   //LINE 494 ERROR 
        perror("validate_date mktime error");
        exit(-1);
    }
    if(datefrom == 0 && dateto == 0) return true; 
    double difference_from, difference_to, difference;
    if(datefrom > 0 && dateto > 0){
        difference_from = difftime(tm_date, datefrom);
        difference_to = difftime(dateto, tm_date);
        if(difference_from>0 && difference_to>0) return true; 
    }
    else if(datefrom > 0 && dateto == 0){
        if((difference = difftime(tm_date, datefrom))>0) return true;
    }
    else if(datefrom == 0 && dateto > 0)
        if((difference = difftime(dateto, tm_date))>0) return true;
    return false;
}

瓦尔格林德错误：

    CalFilter...
temp->value: (20160218T175508Z)
==25873== Conditional jump or move depends on uninitialised value(s)
==25873==    at 0x1002036D6: _st_time1 (in /usr/lib/system/libsystem_c.dylib)
==25873==    by 0x1002039A7: mktime (in /usr/lib/system/libsystem_c.dylib)
==25873==    by 0x100002856: validate_date (main.c:494)
==25873==    by 0x100002B7D: event_date_range (main.c:532)
==25873==    by 0x100002CB7: comp_copy (main.c:559)
==25873==    by 0x100002E15: calFilter (main.c:589)
==25873==    by 0x100003156: main (main.c:647)
==25873== 
temp->value: (20160218T175723Z)
temp->value: (20160218T175816Z)
==25873== Conditional jump or move depends on uninitialised value(s)
==25873==    at 0x100204590: time2sub (in /usr/lib/system/libsystem_c.dylib)
==25873==    by 0x100203927: time2 (in /usr/lib/system/libsystem_c.dylib)
==25873==    by 0x1002036F6: _st_time1 (in /usr/lib/system/libsystem_c.dylib)
==25873==    by 0x1002039A7: mktime (in /usr/lib/system/libsystem_c.dylib)
==25873==    by 0x100002856: validate_date (main.c:494)
==25873==    by 0x100002B7D: event_date_range (main.c:532)
==25873==    by 0x100002CB7: comp_copy (main.c:559)
==25873==    by 0x100002E15: calFilter (main.c:589)
==25873==    by 0x100003156: main (main.c:647)
==25873== 
==25873== Conditional jump or move depends on uninitialised value(s)
==25873==    at 0x10020459C: time2sub (in /usr/lib/system/libsystem_c.dylib)
==25873==    by 0x100203927: time2 (in /usr/lib/system/libsystem_c.dylib)
==25873==    by 0x1002036F6: _st_time1 (in /usr/lib/system/libsystem_c.dylib)
==25873==    by 0x1002039A7: mktime (in /usr/lib/system/libsystem_c.dylib)
==25873==    by 0x100002856: validate_date (main.c:494)
==25873==    by 0x100002B7D: event_date_range (main.c:532)
==25873==    by 0x100002CB7: comp_copy (main.c:559)
==25873==    by 0x100002E15: calFilter (main.c:589)
==25873==    by 0x100003156: main (main.c:647)
==25873== 
temp->value: (20160218T180006Z)
temp->value: (20160218T180026Z)
temp->value: (20160218T180103Z)
temp->value: (20160218T180223Z)
temp->value: (20160218T175604Z)
Test print of copy...
Object: (VEVENT)
Object: (VEVENT)
Object: (VEVENT)
Object: (VEVENT)
Object: (VEVENT)
Object: (VEVENT)
Object: (VEVENT)
Object: (VEVENT)
(DTSTART)
(DTSTART)
(DTSTART)
(DTSTART)
==25873== Invalid read of size 1
==25873==    at 0x100012874: _platform_strcmp (in /usr/local/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==25873==    by 0x100002E66: calFilter (main.c:595)
==25873==    by 0x100003156: main (main.c:647)
==25873==  Address 0x100a8b6f0 is 0 bytes inside a block of size 12 free'd
==25873==    at 0x10001044D: free (vg_replace_malloc.c:534)
==25873==    by 0x1000025AD: calExtract (main.c:429)
==25873==    by 0x100003106: main (main.c:645)
==25873==  Block was alloc'd at
==25873==    at 0x10000FEA1: malloc (vg_replace_malloc.c:303)
==25873==    by 0x100005265: parseCalProp (calutil.c:588)
==25873==    by 0x1000046E2: readCalComp (calutil.c:351)
==25873==    by 0x10000494B: readCalComp (calutil.c:402)
==25873==    by 0x1000049EA: readCalComp (calutil.c:410)
==25873==    by 0x1000049EA: readCalComp (calutil.c:410)
==25873==    by 0x1000049EA: readCalComp (calutil.c:410)
==25873==    by 0x1000049EA: readCalComp (calutil.c:410)
==25873==    by 0x100003AC6: readCalFile (calutil.c:222)
==25873==    by 0x10000300C: main (main.c:634)
==25873== 
(DTSTART)
(DTSTART)
(DTSTART)
(DTSTART)
==25873== Conditional jump or move depends on uninitialised value(s)
==25873==    at 0x100002EF3: calFilter (main.c:606)
==25873==    by 0x100003156: main (main.c:647)
==25873== 
==25873== 

enter code here

Answer 1

从 strptime 手册页：

原则上，此函数不初始化 tm，而只存储 指定的值。这意味着 tm 应该在 叫。

您已调用strptime来填充tm变量。但是，如上面的手册页摘录所述，strptime可能不会在 tm 变量中设置所有字段。所以 valgrind 抱怨tm中的某些字段可以在没有初始化的情况下使用。

所以你的代码需要在调用strptime之前显式初始化它。例如，使用初始化器或使用 memset 。

struct tm tm = { 0 };

或

memset(&tm, 0, sizeof(tm));