C++17 filesystem call generates segmentation fault

Question

Based on the response to Size of file using C++17, I wrote the following program. But, when the executable is run, I get a segmentation fault. I am using g++ 8.3.0 on an iMac running High Sierra.

// c17filesize.cpp
// Jul-02-2019

#include <cstring>
#include <filesystem>
using namespace std;

int main(int argc, char **argv)
{
    char filename[100];
    (argc > 1) ? strcpy(filename, argv[1]) : strcpy(filename, __FILE__);
    auto size = filesystem::file_size(filename);
}

It is not filesystem, but your code segfauls. Always use strncpy, instead of strcpy. Here you don't need either - just use std::string. — Igor R., Jul 02 '19 at 05:58

nivpeled · Answer 1 · 2019-07-03T11:18:55.200

3

Prefer using string (and its contructor) over c style strings.
according https://en.cppreference.com/w/cpp/filesystem/file_size you must specify full path. Did you verify argv[1] holds a full path?
check the file exist before attempting to read its size std::filesystem::exists(filename);
use try and catch sections to catch an exception.

edited Jul 03 '19 at 11:18

answered Jul 02 '19 at 06:16

nivpeled

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(2) - Where does it say that you need a full path? (3),(4) - It's a good advice, but it can't case a segfault. – HolyBlackCat Aug 07 '19 at 20:33

score 2 · Answer 2 · answered Aug 07 '19 at 20:26

2

Just bumped into segfault whilst using std::filesystem:exists.

With GCC 8.3. Had to link with -lstdc++fs to solve the problem.

Note: GCC 9+ solves this problem (https://gcc.gnu.org/gcc-9/changes.html)

answered Aug 07 '19 at 20:26

weber de souza calixto

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score 1 · Accepted Answer · answered Jul 08 '19 at 02:46

1

Compiling with gcc 9.1.0 went through successfully without any qualms.

answered Jul 08 '19 at 02:46

Seshadri R

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C++17 filesystem call generates segmentation fault

3 Answers3