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114 lines
2.9 KiB
Markdown
114 lines
2.9 KiB
Markdown
---
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title: Compiling [MAKE / GCC]
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description:
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draft: false
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tags:
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- c
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- programming
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author: TrudeEH
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showToc: true
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---
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A compiler converts `C` code into machine code in 4 steps:
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1. **Preprocessing** (Convert all preprocessor instructions (`#…`) to C code.)
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2. **Compiling** (Convert `C` code to assembly.)
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3. **Assembling** (Compile the necessary libraries.)
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4. **Linking** (Merge the compiled code with the compiled libraries.)
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## Libraries
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Libraries are pre-written collections of code that can be reused in other programs. On *UNIX* systems, they are usually located in the `/lib/` and `/usr/include` directories.
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### Math.h
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For example, `math.h` is very useful to implement complex arithmetic operations.
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```C
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#include <math.h>
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double A = sqrt(9);
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double B = pow(2, 4);
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int C = round(3.14);
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int D = ceil(3.14);
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int E = floor(3.99);
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double F = fabs(-100);
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double G = log(3);
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double H = sin(45);
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double I = cos(45);
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double J = tan(45);
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```
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### Using Libraries
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To use a library, we first have to include it in the `C` code.
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```C
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#include <cs50.h> // cs50.h library will be included.
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```
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Then, the library must be linked at compile time (unless it is part of the C standard).
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```Shell
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gcc -o hello hello.c -lcs50
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./hello
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```
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## Optimization Flags
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- `-O2` Optimize for speed
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- `-O3` Optimize for speed aggressively
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- `-Os` Optimize for size
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- `-Og` Optimize for debugging
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- `-Oz` Optimize for size aggressively
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## Make
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`Make` Is a build automation tool that automates the process of compiling, linking and building executables.
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An example `Makefile` (for an app using `GTK4`) could be as follows:
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```Makefile
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CC = gcc
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CFLAGS = $(shell pkg-config --cflags gtk4)
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LIBS = $(shell pkg-config --libs gtk4)
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hello: hello.c
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$(CC) $(CFLAGS) -o hello hello.c $(LIBS) -O2
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debug: hello.c
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$(CC) $(CFLAGS) -o hello hello.c $(LDFLAGS) -Wall -Wextra -Og -g
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clean:
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rm -f hello
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```
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```Shell
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make # Compiles hello.c
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make debug # Compiles hello.c using debug flags
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make clean # Removes the executable (hello) generated by the make command.
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```
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## Meson
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While `make` automates compiling, on larger projects, makefiles can grow hard to read quickly, and dependency resolution has to be done using external tools (such as `pkg-config`).
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Meson is a more modern alternative, which is faster, and uses declarative syntax (describe *what* to build, instead of *how* to build it). Meson can automatically manage dependencies, header files, and compiler flags.
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When `meson` is executed, it generates a `ninja.build` file, which is then parsed by `ninja`, a lower-level build tool.
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```meson.build
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project('hello', 'c')
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gtk4_dep = dependency('gtk4')
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executable('hello', 'hello.c',
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dependencies: gtk4_dep)
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```
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```bash
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mkdir build
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meson setup build # Generate files for Ninja in the build dir
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meson compile -C build # Compile the project (same as `ninja -C build`)
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./build/hello
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ninja clean -C build # Clean executable files in the build directory
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```
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