stack corruption with big write

[Sumenia]

I'm getting a libc: stack corruption detected when using MemoryWriter::write("{}", msg) with a big (> 5k) string as msg.

This is happening on Android (Nougat).

any idea ?

[vitaut]

Could you post a reproducible example?

[Sumenia]

Ok I ran some experiments and found out that this code reproduces the problem :

   std::string msg;

    for (uint32_t i = 0; i < 5420; ++i) {
        msg += "s";
    }

    fmt::MemoryWriter writer;
    writer.clear();
    writer << "info";
    writer << msg;

This depends on the calling context (either if this code is split between functions or not, etc).

The writer << "info"; is important as the code works fine without it.

The stack corruption only appears on the next function return.

edit : forgot to mention that this problem doesn't occur on Linux

[vitaut]

Does it happen on the latest master?

[Quentin01]

Not the last commit on master but the previous one 789ebea8637cce4a7deef.

[vitaut]

I've traced your example code in the debugger and don't see anything that might cause stack corruption. However, note that MemoryWriter uses an inline buffer of size 500 chars, which can cause problems if the stack size limit is small. If this is the case you can use StringWriter instead.

[vitaut]

Might be related to #491 which has just been fixed.