[Solved] lto1: fatal error: bytecode stream..generated with LTO version 6.2 instead of the expected 8.1

[Solved] lto1: fatal error: bytecode stream..generated with LTO version 6.2 instead of the expected 8.1

Author: Amresh Mishra | Published On: February 23, 2024

lto1: fatal error coming in ubuntu Compile libxml2-2.9.1 in ./configure & make & make install

lto1: fatal error:

lto1: fatal error: bytecode stream in file ‘/home/…/anaconda3/envs/rasa/lib/python3.6/config-3.6m-x86_64-linux-gnu/libpython3.6m.a’ generated with LTO version 6.2 instead of the expected 8.1
compilation terminated.
lto-wrapper: fatal error: gcc returned 1 exit status
compilation terminated.
/usr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status
make[4]: *** [Makefile:519: libxml2mod.la] Error 1
make[4]: Leaving directory ‘/home/…/libxml2-2.9.1/python’
make[3]: *** [Makefile:607: all-recursive] Error 1
make[3]: Leaving directory ‘/home/…/libxml2-2.9.1/python’
make[2]: *** [Makefile:450: all] Error 2
make[2]: Leaving directory ‘/home/…/libxml2-2.9.1/python’
make[1]: *** [Makefile:1304: all-recursive] Error 1
make[1]: Leaving directory ‘/home/…/libxml2-2.9.1’
make: *** [Makefile:777: all] Error 2

lto1: fatal error Solution :

 To solve this you need to do-

conda install -c anaconda gcc_linux-64

Also Read: https://coderscanteen.com/sun-security-pkcs-not-found/

Ah, the joys of programming! There you are, diligently working on your project, everything seems to be going smoothly, and then BAM! You hit a wall. This time, the wall’s name is “lto1: fatal error: bytecode stream..generated with LTO version 6.2 instead of the expected 8.1.” Now, before you hurl your computer out the window or drown your sorrows in a gallon of ice cream, take a deep breath. We’re here to help you navigate this pesky issue and get your code back on track.

Understanding the Error

To understand why this error occurs, let’s break it down a bit. The message “lto1: fatal error: bytecode stream..generated with LTO version 6.2 instead of the expected 8.1” is quite a mouthful, isn’t it? But don’t worry, it’s not as scary as it sounds. Essentially, this error means that the bytecode (a kind of intermediate code) was generated using a different version of Link Time Optimization (LTO) than what your current toolchain expects.

[Solved] lto1: Fatal Error: Bytecode Stream...Generated with LTO Version 6.2 Instead of the Expected 8.1

What is LTO?

Link Time Optimization (LTO) is a method used to optimize a program by performing optimizations at link time rather than compile time. This can result in more efficient code because the optimizer has a complete view of the program. Think of it like this: if compiling is like putting together the pieces of a puzzle, LTO is like looking at the entire picture on the box to make sure everything fits perfectly.

Why Does This Error Occur?

The root of the problem is version mismatch. Your compiler expects one version of LTO, but it gets another. It’s like asking for a chocolate ice cream cone and getting vanilla instead. Sure, both are ice creams, but it’s not what you were expecting.

Solving the Error

Alright, let’s roll up our sleeves and fix this problem. Here’s a step-by-step guide to resolving the “lto1: fatal error: bytecode stream..generated with LTO version 6.2 instead of the expected 8.1” error.

1. Check Your Toolchain Versions

The first thing you need to do is verify the versions of your toolchain. This includes your compiler (GCC, Clang, etc.) and other related tools.

  • GCC: Use gcc --version to check your GCC version.
  • Clang: Use clang --version to check your Clang version.

Make sure that all parts of your toolchain are compatible with each other. If you’re using an older version of GCC, it might be time for an upgrade.

2. Update Your Compiler

If your compiler is outdated, updating it might solve the problem. Here’s how you can update GCC:

sudo apt-get update
sudo apt-get install gcc

For Clang, you can use:

sudo apt-get update
sudo apt-get install clang

Make sure you’re installing the latest stable version.

3. Check Your Makefile or Build Scripts

If you’re using a Makefile or any other build script, double-check the configurations. Sometimes, the version mismatch could be due to hardcoded paths or specific flags that are outdated.

4. Clean Your Build Environment

Sometimes, old build files can cause conflicts. Cleaning your build environment can help ensure that all files are compiled with the correct settings.

make clean

This will remove any old build files and recompile everything from scratch.

5. Rebuild All Dependencies

If you’re working on a larger project with multiple dependencies, make sure all dependencies are built with the same toolchain version. Rebuilding all dependencies ensures consistency.

make clean
make all

A Funny Anecdote

Here’s a little story to lighten the mood. Imagine you’re a chef, and you’re trying to make a cake. You ask your assistant to bring you flour, sugar, and eggs. But instead, they bring you flour, sugar, and pickles. Sure, pickles are food, but they definitely don’t belong in a cake! The version mismatch error is a bit like that – you’re expecting one thing, but you get something completely different. And while it might be frustrating, at least it’s not as bad as a pickle cake!


Q: What if I’m still getting the error after updating my toolchain?

A: Double-check that all parts of your toolchain are updated. Sometimes, you might have multiple versions of a tool installed, and your build system might be using the wrong one.

Q: Can I use a different version of LTO?

A: It’s best to use the version that matches your toolchain. Mixing versions can lead to unpredictable results.

Q: I don’t have admin privileges on my system. How can I update my compiler?

A: You can install a newer version of the compiler in your home directory. Many compilers offer a way to install locally without needing admin privileges.

Q: Is there a way to disable LTO?

A: Yes, you can disable LTO by modifying your build settings. However, this might affect performance. Use flags like -fno-lto to disable it.

Q: What if I’m using a package manager like Homebrew or APT?

A: Ensure that your package manager is up to date. Sometimes, package managers might have older versions of software, so check for the latest updates.


Dealing with the “lto1: fatal error: bytecode stream..generated with LTO version 6.2 instead of the expected 8.1” error can be frustrating, but it’s definitely solvable. By understanding what LTO is, why the error occurs, and following the steps to fix it, you can get back to coding without tearing your hair out. Remember, programming is a journey with its fair share of bumps along the way, but with patience and perseverance, you’ll overcome any obstacle.

And hey, if all else fails, take a break, grab a snack, and come back to it with fresh eyes. Sometimes, a little humor and a clear mind are all you need to tackle the toughest problems.

Final Thoughts

In the world of programming, errors are like plot twists in a novel. They can be unexpected, frustrating, and sometimes downright confusing. But they also make the journey interesting and provide opportunities to learn and grow. So the next time you encounter an error like “lto1: fatal error: bytecode stream..generated with LTO version 6.2 instead of the expected 8.1,” remember that it’s just a part of the adventure.

Keep calm, code on, and may your bugs be few and your solutions be swift!

If you’ve found this guide helpful, feel free to share it with your fellow developers. After all, a shared problem is a problem halved. Happy coding!

Author: Amresh Mishra
Amresh Mishra is a passionate coder and technology enthusiast dedicated to exploring the vast world of programming. With a keen interest in web development, software engineering, and emerging technologies, Amresh is on a mission to share his knowledge and experience with fellow enthusiasts through his website, CodersCanteen.com.

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