# Compilation and Building Subsystem
## Mini and Small Systems
### Invalid -- w Option
- **Symptom**
The build fails, and "usr/sbin/ninja: invalid option -- w" is displayed.
- **Cause**
The Ninja version in the build environment is outdated and does not support the **--w** option.
- **Solution**
Uninstall Ninja and GN and follow the instructions provided in [IDE](../get-code/gettools-ide.md) to install Ninja and GN of the required version.
### Library ncurses Not Found
- **Symptom**
The build fails, and "/usr/bin/ld: cannot find -lncurses" is displayed.
- **Cause**
The ncurses library is not installed.
- **Solution**
```
sudo apt-get install lib32ncurses5-dev
```
### mcopy not Found
- **Symptom**
The build fails, and "line 77: mcopy: command not found" is displayed.
- **Cause**
mcopy is not installed.
- **Solution**
```
​sudo apt-get install dosfstools mtools
```
### No riscv File or Directory
- **Symptom**
The build fails, and the following information is displayed:
riscv32-unknown-elf-gcc: error trying to exec 'cc1': execvp: No such file or directory.
- **Cause**
Permission is required to access files in the **riscv** compiler directory.
- **Solution**
Run the following command to query the directory where **gcc\_riscv32** is located:
```
which riscv32-unknown-elf-gcc
```
Run the **chmod** command to change the directory permission to **755**.
### No Crypto
- **Symptom**
The build fails, and "No module named 'Crypto'" is displayed.
- **Cause**
Crypto is not installed in Python 3.
- **Solution**
1. Run the following command to query the Python version:
```
python3 --version
```
2. Ensure that Python 3.7 or later is installed, and then run the following command to install pycryptodome:
```
sudo pip3 install pycryptodome
```
### Unexpected Operator
- **Symptom**
The build fails, and "xx.sh \[: xx unexpected operator" is displayed.
- **Cause**
The build environment is shell, not bash.
- **Solution**
```
sudo rm -rf /bin/sh
sudo ln -s /bin/bash /bin/sh
```
### What should I do when the message **Could not find a version that satisfies the requirement six\>=1.9.0** is displayed during compilation and building?
- **Symptom**
The following error occurs during compilation and building:
```
Could not find a version that satisfies the requirement six>=1.9.0
```
- **Possible Causes**
**six** is not installed.
- **Solutions**
Solution 1: Run the **pip3 install six** command to install **six** online.
Solution 2: Install **six** offline.
- Download the installation package from [https://pypi.org/project/six/\#files](https://pypi.org/project/six/#files).
- Save the source code to the Linux server and run the **pip3 install six-1.14.0-py2.py3-none-any.whl** command to install **six**.
- Rebuild an environment.
### What should I do when the message **cannot find -lgcc** is displayed during compilation and building?
- **Symptom**
The following error occurs during compilation and building:
```
riscv32-unknown-elf-ld: cannot find -lgcc
```
- **Possible Causes**
The PATH is incorrectly written by **gcc\_riscv32**. There is an extra slash \(/\).
```
~/gcc_riscv32/bin/:/data/toolchain/
```
- **Solutions**
Modify the PATH by deleting the slash \(/\).
```
~/gcc_riscv32/bin:/data/toolchain/
```
### What should I do when the message indicating Python cannot be found is displayed during compilation and building?
- **Symptom**
The following error occurs during compilation and building:
```
-bash: /usr/bin/python: No such file or directory
```
- **Possible Cause 1:** Python is not installed.
- **Solutions**
[Install Python](../quick-start/quickstart-lite-env-setup-linux.md).
- **Possible Cause 2:** The soft link that points to the Python does not exist in the **usr/bin** directory.
- **Solutions**
Run the following commands to add a soft link:
```
# cd /usr/bin/
# which python3
# ln -s /usr/local/bin/python3 python
# python --version
```
Example:
### What should I do when the message indicating Python 3 cannot be found is displayed during compilation and building?
- **Symptom**
- **Possible Causes**
Python 3 is not installed.
- **Solutions**
[Install Python](../quick-start/quickstart-lite-env-setup-linux.md).