144 lines
3.2 KiB
Markdown
144 lines
3.2 KiB
Markdown
# C++ with Clang & Make — Cheat Sheet
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## Writing C++
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A basic C++ file (`hello.cpp`):
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```cpp
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#include <iostream>
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int main() {
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std::cout << "Hello, world!" << std::endl;
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return 0;
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}
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```
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## Compiling with Clang
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| Command | What it does | Example |
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|---------|-------------|---------|
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| clang++ <file> | Compile to an executable named a.out | clang++ hello.cpp |
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| clang++ <file> -o <name> | Compile and name the output | clang++ hello.cpp -o hello |
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| clang++ -Wall <file> | Enable **all** warnings (always use this!) | clang++ -Wall hello.cpp -o hello |
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| clang++ -std=c++17 <file> | Use a specific C++ version | clang++ -std=c++20 -Wall prog.cpp -o prog |
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| clang++ -g <file> | Include debug info (for use with a debugger) | clang++ -g -Wall hello.cpp -o hello |
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**Common flags explained:**
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| Flag | Meaning |
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|------|---------|
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| -o <name> | Output filename (instead of a.out) |
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| -Wall | Enable most compiler warnings |
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| -Wextra | Enable even more warnings |
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| -std=c++17 | Use C++17 standard (also c++11, c++14, c++20) |
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| -g | Include debug symbols (for gdb or lldb) |
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| -O2 | Optimize for speed |
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### Full compile example
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```bash
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clang++ -Wall -Wextra -std=c++20 my_program.cpp -o my_program
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./my_program
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```
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## Running Your Program
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```bash
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./my_program # Run it
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./my_program arg1 # Pass a command-line argument
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```
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## Make & Makefiles
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`make` automates your build so you don't have to type long `clang++` commands.
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### Example project structure
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```
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project/
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├── Makefile
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├── main.cpp
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├── helpers.cpp
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└── helpers.hpp
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```
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### Minimal Makefile
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```make
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hello: hello.cpp
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clang++ -Wall -std=c++17 hello.cpp -o hello
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```
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**⚠️ The indented line must use a Tab, not spaces.**
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### Building with make
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```bash
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make # Build the first target
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make hello # Build the target named 'hello'
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```
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### Better Makefile with variables
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```make
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CXX = clang++
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CXXFLAGS = -Wall -Wextra -std=c++20
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TARGET = my_program
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$(TARGET): main.cpp helpers.cpp helpers.hpp
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$(CXX) $(CXXFLAGS) main.cpp helpers.cpp -o $(TARGET)
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clean:
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rm -f $(TARGET)
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.PHONY: clean
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```
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| Command | What it does |
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|---------|-------------|
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| make | Build the program |
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| make clean | Delete the compiled program |
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| make -j4 | Build using 4 CPU cores (faster) |
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### Typical Makefile with separate compilation
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```make
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CXX = clang++
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CXXFLAGS = -Wall -Wextra -std=c++20
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TARGET = my_program
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OBJECTS = main.o helpers.o
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$(TARGET): $(OBJECTS)
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$(CXX) $(OBJECTS) -o $(TARGET)
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main.o: main.cpp helpers.hpp
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$(CXX) $(CXXFLAGS) -c main.cpp -o main.o
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helpers.o: helpers.cpp helpers.hpp
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$(CXX) $(CXXFLAGS) -c helpers.cpp -o helpers.o
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clean:
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rm -f $(TARGET) $(OBJECTS)
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.PHONY: clean
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```
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## Quick Reference — Common Workflow
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```bash
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# 1. Write your code
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nano hello.cpp
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# 2. Compile
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clang++ -Wall -std=c++20 hello.cpp -o hello
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# 3. Run
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./hello
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# Or use a Makefile
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make
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./hello
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```
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## Tips
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- Always compile with `-Wall` — warnings catch bugs!
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- Use `-std=c++20` to get modern C++ features (`auto`, `ranges`, `std::span`, etc.)
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- If `clang++` isn't installed: `sudo apt install clang`
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- If `make` isn't installed: `sudo apt install make`
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- When editing Makefiles: **rules must be indented with a Tab character**
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