Problems with std::string.replace()

[ywbpSL3A]

I'm trying to write a function, which replaces all occurrences of a std::string with a different one. Naturally, I tried using std::string.replace() as a first bet but that doesn't seem to be working.

#include <string>

void Func( std::string &s, const std::string &oldVal, const std::string &newVal ) {
    auto curr = s.cbegin();

    while ( curr <= ( s.cend() - oldVal.size() ) ) {
        if ( std::string( curr, curr + oldVal.size() ) == oldVal ) {
            s.replace( curr, curr + oldVal.size(), newVal );

            curr += newVal.size();
        } else {
            ++curr;
        }
    }
}

int main() {
    std::string success = "i went thru a river, thru a deep forest";
    Func( success, "thru", "through" );

    std::string error = "i went thru a river, thru it was quite deep";
    Func( error, "thru", "through" );

    return 0;
}

What is causing the second std::string to output:

cannot seek string iterator because the iterator was invalidated (e.g. reallocation occured, or the string was destroyed)

? Should I rather use std::string.insert() and std::string.erase() to properly update the iterator curr?

[z05DSL3A]

Try...

#include <iostream>
#include <string>

void Func (std::string& str, const std::string& oldStr, const std::string& newStr) {
    std::string::size_type pos = 0u;
    while ((pos = str.find (oldStr, pos)) != std::string::npos) {
        str.replace (pos, oldStr.length (), newStr);
        pos += newStr.length ();
    }
}

int main () {
    std::string success = "i went thru a river, thru a deep forest";
    Func (success, "thru", "through");

    std::cout << success << "\n\n";

    std::string error = "i went thru a river, thru it was quite deep";
    Func (error, "thru", "through");

    std::cout << error << "\n\n";

    return 0;
}