Question

我正在从一份研究论文中运行open source code，遇到了分段错误错误。

我使用gdb来查看生成的核心文件，并使用bt full来了解出了什么问题，但是我对c ++还是很陌生，所以我不知道如何使用提供的信息进一步调试此错误。

Program terminated with signal SIGSEGV, Segmentation fault.
#0  __GI_____strtof_l_internal (nptr=0x0, endptr=0x7ffecd484cd8, group=<optimized out>, loc=0x7f32914c5560 <_nl_global_locale>)
    at strtod_l.c:609
609 strtod_l.c: No such file or directory.
(gdb) bt full
#0  __GI_____strtof_l_internal (nptr=0x0, endptr=0x7ffecd484cd8, group=<optimized out>, loc=0x7f32914c5560 <_nl_global_locale>)
    at strtod_l.c:609
        negative = 0
        num = {0, 0, 0, 511101108348, 390842024046, 0, 0, 4, 18446744073709551504, 140732342488280}
        numsize = 0
        exponent = 0
        base = 10
        den = {140732342488280, 0, 4, 139855159296252, 139855168706208, 0, 14395410707824902144, 4, 140732342488288, 139855165608536}
        densize = <optimized out>
        retval = {206158430210}
        bits = 0
        cp = 0xffffffffffffffff <error: Cannot access memory at address 0xffffffffffffffff>
        tp = <optimized out>
        startp = <optimized out>
        start_of_digits = <optimized out>
        expp = <optimized out>
        dig_no = <optimized out>
        int_no = <optimized out>
        lead_zero = <optimized out>
        c = <optimized out>
        decimal = 0x7f329128e7d8 <dot> "."
        decimal_len = 1
        thousands = 0x0
        grouping = 0x0
        cnt = <optimized out>
        current = <optimized out>
        __PRETTY_FUNCTION__ = "____strtof_l_internal"
        lowc = <optimized out>
#1  0x0000562b2bf93133 in get_all_cooked_time_bw(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >) ()
No symbol table info available.
#2  0x0000562b2bf8f2ab in main ()
No symbol table info available.
(gdb) quit

我猜这是哪里出了问题： cp = 0xffffffffffffffff <error: Cannot access memory at address 0xffffffffffffffff>，但是我不知道cp代表什么，在哪里以及如何解决这个问题。

以下是相关代码：

void split(const std::string &s, char delim, std::vector<std::string> &elems) {
    std::stringstream ss;
    ss.str(s);
    std::string item;
    while (std::getline(ss, item, delim)) {
        elems.push_back(item);
    }
}

std::vector<std::string> split(const std::string &s, char delim) {
    std::vector<std::string> elems;
    split(s, delim, elems);
    return elems;
}

ALL_COOKED_TIME_BW get_all_cooked_time_bw(std::string path) {
    ALL_COOKED_TIME_BW all_cooked_time_bw;
    struct dirent *entry;
    DIR *dir = opendir(path.c_str());
    if (dir != NULL) {
        while ((entry = readdir(dir)) != NULL) {
            if (entry->d_name[0] == '.') continue;  // read . or ..

            std::string file_name = "";
            file_name += COOKED_TRACE_FOLDER;
            file_name += entry->d_name;
            printf("%s\n", file_name.c_str());

            std::ifstream in_file(file_name);
            std::string line;
            std::vector<float> cooked_time;
            std::vector<float> cooked_bw;

            if (in_file.is_open())
            {

                while ( getline (in_file, line) )
                {
                    std::vector<std::string> parse = split(line, '\t');
                    cooked_time.push_back(std::stof(parse[0]));
                    cooked_bw.push_back(std::stof(parse[1]));
                }
                in_file.close();
            }

            all_cooked_time_bw.all_cooked_time.push_back(cooked_time);
            all_cooked_time_bw.all_cooked_bw.push_back(cooked_bw);
            all_cooked_time_bw.all_file_names.push_back(entry->d_name);

        }
    }
    closedir(dir);

    return all_cooked_time_bw;
}

Answer 1

如果此处传递给split的行不包含2个（或更多）元素：

std::vector<std::string> parse = split(line, '\t');

然后，以下两行通过将无效的字符串传递给std::stof导致未定义的行为：

cooked_time.push_back(std::stof(parse[0]));
cooked_bw.push_back(std::stof(parse[1]));

这应该通过一些更具防御性的编程来解决：

if ( parse.size() != 2 )
{
   throw std::invalid_argument("invalid file: " + file_name);
}
cooked_time.push_back(std::stof(parse[0]));
cooked_bw.push_back(std::stof(parse[1]));

在大多数情况下，您还应该将pos参数传递给std::stof，否则它将忽略字符串末尾的非数字字符。例如：

size_t pos;
cooked_time.push_back(std::stof(parse[0], &pos));
if (pos != parse[0].size())
{
   throw std::invalid_argument("invalid file: " + file_name);
}

如何修复SIGSEGV细分错误？

1 个答案: