Common errors

g++ messages start with the file and line. Template errors can be long: read the first error: line, then look for the line in your own file.

• error: 'x' was not declared in this scope — a typo, a variable from another block, a missing #include, or a missing std::.
• error: no matching function for call to … — the argument types do not fit any version of the function; the notes below list what was tried.
• error: no match for 'operator<<' — printing a type that has no << (for example a whole std::vector); print its elements in a loop.
• undefined reference to … — declared but never defined: a missing .cpp file, or one whose name starts with main/test_.
• terminate called after throwing an instance of 'std::out_of_range' — an uncaught exception, here from .at() or std::stoi.
• g++: internal compiler error: File size limit exceeded — the compiler's intermediate output for one source file is over the run's 1 MB file-size limit. It happens with several heavy headers in one file (<regex> and <format> together, for example). Move part of the code into another .cpp file: each file is compiled separately.
• Exit code 139 (signal 11, segmentation fault) — an index past the end with [], a null or dangling pointer, or a reference to a destroyed object.

#include <iostream>
#include <stdexcept>
#include <string>
#include <vector>

int main() {
    std::vector<std::string> values{"10", "x", "7"};
    int total = 0;
    for (const auto& v : values) {
        try {
            total += std::stoi(v);
        } catch (const std::invalid_argument&) {
            std::cout << "skipped " << v << '\n';
        }
    }
    std::cout << "total: " << total << '\n';
}

skipped x
total: 17