Compilers

• .

GCC (GNU C Compiler -> GNU Compiler Collection)

About

• Originally, the name was "GNU C Compiler" because it only compiled the C language. Over time, it began to support other languages and was renamed "GNU Compiler Collection".

• Part of the GNU project; widely used in Linux. Supports multiple languages.

• License :

  • Open-source GPL.

• Platforms :

  • Windows (via MinGW), Linux, macOS, BSD

• Debugging

  • GDB.

• Minimum requirements :

  • Windows:

    • MinGW.

    • ~MSYS2.

      • You don't need MSYS2 to use GCC on Windows. MinGW already provides GCC ready to use.

      • MSYS2 is an additional environment that facilitates installation and package management, but it is not mandatory.

  • Linux:

    • Just the package.

gcc -o main main.c

gcc -o main main.c random.c -lm

• GCC Explanation {1:20 -> 5:33} .

Installing

• Version :

  • (2025-06-13) 14.2.0

• Choosing a Toolchain and Runtime :

  • For Linux :

    • .

  • For Windows :

    • I stay away from MSVC, as it's a Windows thing.

    • Via MSYS2 without MSVC :

      • MSYS2 Download

      • All three use MinGW (GNU) ABI , so no MSVC dependency.

      • UCRT64 : pacman -S mingw-w64-ucrt-x86_64-gcc

        • Compiler : GCC

        • ABI : MinGW (GNU)

        • Runtime : UCRT

        • Environment : UCRT64

        • Architecture : x86_64

        • Installed at : C:/msys64/ucrt64/bin .

        • Modern setup; recommended GCC on Windows.

      • MINGW64 : pacman -S mingw-w64-x86_64-gcc

        • Compiler : GCC

        • ABI : MinGW (GNU)

        • Runtime : MSVCRT

          • It's a very old Microsoft runtime, outdated (missing newer C features, UTF-8 issues)

          • Legacy, very compatible.

        • Environment : MINGW64

        • Architecture : x86_64

        • Installed at : C:/msys64/mingw64/bin .

      • CLANG64

        • GCC is not typically used in CLANG64.

        • The environment is designed around Clang/LLVM.

Commands

• -o

  • Sets the name of the output file.

• -std=c11

  • Specify Language Standard.

  • C89, C99, C11, C17, etc.

  • -ansi

    • Forces compliance with C89/C90.

• Compilation :

  • -c

    • Compile without linking, creating the object file .o  / .obj .

  • -v

    • Verbose mode (shows compilation steps).

• Linking :

  • -l<name>

    • Link with a library.

    • -lm

      • Link with the Math Library libm .

        • Needed for functions like sin() , cos() , sqrt() , pow() , etc.

    • -lpthread .

      • For threads.

  • -L<path>

    • Adds a library directory.

    • -L./lib .

  • -static

    • Link statically (avoids dynamic dependencies).

  • -shared

    • Generates a shared library ( .so  / .dll ).

  • -fPIC

    • Generates position-independent code (used in shared libs).

• Pre-processor / Macro :

  • -I<path>

    • Adds an include directory.

    • -I./include .

      • Looks for headers in ./include .

  • -D<macro>

    • Defines a macro (ex: -DDEBUG  is equivalent to define DEBUG ).

  • -U<macro>

    • Undefines a macro.

  • -E

    • Only preprocesses (outputs include  and define  results).

  • -M

    • Generates build dependencies (useful for Makefiles).

• Debug :

  • -g

    • Includes debug symbols (needed for gdb  and valgrind ).

  • -ggdb

    • Optimizes debug symbols for GDB  (more detailed than -g ).

  • -fsanitize=address

    • Detects memory leaks, buffer overflows (AddressSanitizer).

  • -fsanitize=undefined

    • Detects undefined behavior (UB).

  • -fstack-protector

    • Protection against stack smashing.

  • -fno-stack-protector

    • Disables stack overflow protection.

• Warnings / Errors :

  • -Wall

    • Enable Compilation Warnings.

  • -Wextra

    • Enables extra warnings beyond -Wall .

  • -Wpedantic

    • Enforces strict C standard compliance (complains about GNU extensions).

  • -Wno-warning_name

    • Disables a specific warning (ex: -Wno-unused-variable ).

  • -Werror

    • Treat Warning as Errors.

• Optimizations :

  • -O0

    • No optimization (better for debugging).

  • -O1 , -O2 , -O3

    • Levels of code optimization. Higher = faster, but harder to debug.

  • -Os

    • Optimization for size (reduces executable).

  • -Ofast

    • Aggressive optimization + relaxes IEEE standards (may affect precision).

Clang/LLVM (Low-Level Virtual Machine)

About

• Clang/LLVM gives you :

  • C/C++ frontend (clang, clang++)

  • Optimizer (LLVM IR passes)

  • Code generation (machine code)

  • Optional linker (lld)

• LLVM/Clang is not a complete toolchain by itself—it is mainly a compiler frontend + optimizer + code generator.

• What it doesn't give you :

  • Standard libraries

    • C standard library (libc)

    • C++ standard library (libc++ or libstdc++)

  • Platform runtime

    • Startup code (mainCRTStartup, etc.)

    • Exception handling

    • Threading support

    • These are platform-specific and not provided by LLVM itself.

  • System headers

    • stdio.h , windows.h , etc.

    • Definitions for OS APIs

  • System libraries

    • Windows APIs (kernel32.lib, etc.)

    • Required for linking executables

• To get what is missing :

  • For windows:

    • MSVC toolchain

      • Microsoft’s C runtime (MSVCRT / UCRT)

      • Windows SDK headers/libs

      • Linker and startup code

    • MinGW / MSYS2

      • GCC-compatible runtime

      • Open-source Windows headers/libs

      • GNU-style environment

• About LLVM with MSVC :

  • I don't like it, as it's a Windows thing.

  • lld-link:

    • Is LLVM’s drop-in replacement for the MSVC linker (link.exe)

    • So when you see lld-link: error ... , it means Clang is operating in MSVC mode.

  • For libs:

    • It uses MSVC conventions, like:

      • .lib libraries

      • no lib prefix

    • COFF format expectations
      | Mode        | Expected file |
      | ----------- | ------------- |
      | MSVC        | raylib.lib   |
      | GNU (MinGW) | libraylib.a  |

• It is not a single package but a collection of modular tools and libraries  for compilation. It forms a complete compilation infrastructure, which can include multiple related components.

• Depending on the distribution or installation method, not all components may be included.

• Packages :

  • llvm

  • clang

  • clang-tools-extra

  • flang

  • mlir

  • lld

  • lldb

  • polly

  • libLTO

  • compiler-rt

  • libunwind

  • libc++

  • lib++abi

  • openmp

  • llvm-ar

  • llvm-nm

  • llvm-objdump

  • llvm-cov

  • llvm-profdata

  • llvm-dwarfdump

  • llvm-symbolizer

  • wasm-ld

• High compatibility with GCC.

• License :

  • Open-source Apache 2.0.

• Platforms :

  • Windows, Linux, macOS, BSD

• Debugging

  • LLDB.

    • More modern than GDB.

• Minimum requirements :

  • Windows / Linux / macOS:

    • LLVM.

• LLVM .

• .

• LLVM explained .

  • Cool.

• LLVMIR explanation and demonstration

  • "IR is much more verbose by default, to allow for some specific optimizations".

• How to compile C++ with clang in VSCode .

Installation

• Version :

  • llvm-config --version

  • (2025-06-13) 21.1.7

• Install LLVM or Clang?

  • llvm

    • Backend + toolchain infrastructure

    • Only if you need LLVM tools directly

  • clang

    • Actual compiler (frontend)

    • If you want to compile code

• Choosing a Toolchain and Runtime :

  • For Linux :

    • llvm-project/releases

  • For Windows :

    • I stay away from MSVC, as it's a Windows thing.

    • Via MSYS2 without MSVC :

      • MSYS2 Download

      • All three use MinGW (GNU) ABI , so no MSVC dependency.

      • A installation can be removed with pacman -Rs <name>

      • UCRT64 : pacman -S mingw-w64-ucrt-x86_64-clang

        • Compiler : Clang (LLVM)

        • ABI : MinGW (GNU)

        • Runtime : UCRT

        • Environment : UCRT64

        • Architecture : x86_64

        • Installed at : C:/msys64/ucrt64/bin .

        • Size : 1112MB

        • Modern setup; recommended for non-MSVC Clang on Windows.

      • CLANG64 : pacman -S mingw-w64-clang-x86_64-clang

        • Compiler : Clang (LLVM)

        • ABI : MinGW (GNU)

        • Runtime : UCRT

        • Environment : CLANG64

        • Architecture : x86_64

        • Installed at : C:/msys64/clang64/bin .

        • Size : 900.7MB

        • (2026-04-03) It didn't install correctly the clang.exe  in Paola's PC.

      • MINGW64 : pacman -S mingw-w64-x86_64-clang

        • Compiler : Clang (LLVM)

        • ABI : MinGW (GNU)

        • Runtime : MSVCRT

          • It's a very old Microsoft runtime, outdated (missing newer C features, UTF-8 issues)

          • Legacy, very compatible.

        • Environment : MINGW64

        • Architecture : x86_64

        • Installed at : C:/msys64/mingw64/bin .

    • Via LLVM-MinGW :

      • llvm-mingw/releases

        • llvm-mingw-20260324-ucrt-x86_64.zip .

          • Compiler : Clang (LLVM)

          • ABI : MinGW (GNU)

          • Runtime : UCRT runtime

          • Environment : MINGW64

          • Architecture : x86_64

          • Installed at : manual install.

          • Size : 704MB.

    • LLVM-Project

      • Installs with MSVC.

      • llvm-project/releases

      • Release: LLVM-22.1.2-win64.exe

        • Installs x86_64-pc-windows-msvc .

        • (2026-04-04) Not added to PATH, even tho I marked the option to do it.

      • clang+llvm-22.1.2-x86_64-pc-windows-msvc.tar.xz

        • Installs x86_64-pc-windows-msvc .

        • A zip, not the installer, therefore not automatically added to the path.

  • For macOS :

    • On macOS you don’t need an MSYS2-style environment. The system already has a Clang-based toolchain provided by Apple.

    • xcode-select --install

    • This installs the Command Line Tools, which include:

      • clang  / clang++

      • lldb

      • make , git , etc.

      • macOS SDK headers

• The corresponding path of installation has to be added to the PATH.

Commands

• The vast majority of all commands are exactly the same  as GCC.

• Exclusive to Clang :

  • -fcolor-diagnostics

    • Displays colored errors/warnings (great for readability).

  • -Weverything

    • Enables all warnings (even the most pedantic).

  • -MJ <file.json>

    • Generates JSON output for analysis tools (ex: IDEs).

Opinions

• Ginger Bill:

  • I wish I never used LLVM in the first place.

  • It has been the vast majority of the bugs in the Odin compiler.

  • It's slow as fuck, even for development builds.

  • And it gets worse with each release.

  • It's alluring because it's free and is the basis of clang.

• Jonathan Blow:

  • JAI uses LLVM for release builds, but not for debug builds.

  • JBlow - LLVM is cumbersome and slow

Making a language

• Language Frontend with LLVM

  • "The parser we will build uses a combination of Recursive Descent Parsing and Operator-Precedence Parsing to parse the Kaleidoscope language (the latter for binary expressions and the former for everything else)".

  • AST Code .

• LLVM Lexicon

• Dmitry Soshnikov - LLVM Tutorial .

  • Most of the time he's making a very simple code, but making it sound so confusing due to excessive OOP and C++.

  • He didn't finished the tutorials; there's only 5/20 lectures so far.

• Toby Ho - LLVM Tutorial .

  • He follows the Language Frontend with LLVM  line by line in C++, without much explanation.

LLVM Global Context

• It owns and manages the core "global" data of LLVM's core infrastructure, including the types and constant unique tables.

Tilde Backend (TB)

• Tilde Backend

• Tilde Backend

MSVC (Microsoft Visual C++)

• It is the default compiler for Visual Studio.

• cl.exe  (MSVC).

• License :

  • Microsoft proprietary.

• Platforms :

  • Windows / Linux.

• Languages :

  • Limited support for C11/C17

• Requirements :

  • Windows:

    • Install Visual Studio (Community Edition is free).

    • Or maybe the Build Tools.

      • Honestly, you will have to download Visual Studio anyway.

  • Linux:

    • Limited support (using clang-cl  or WSL).

• My version :

  • 14.42.34433 (came with Visual Studio).

  • Had to add C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.42.34433\bin\Hostx64\x64  to the global PATH environment variable.

Commands

• GCC or Clang equivalents :

  • .

• MSVC-specific :

  • /MD  vs /MT

    • Chooses runtime: shared DLL ( /MD ) or static ( /MT ).

  • /EHsc

    • Enables C++ exceptions (default in C++ projects).

  • /JMC

    • Supports "Just My Code" in the debugger.

  • /MP

    • Parallel compilation (speeds up large builds).

// Equivalent to `gcc -o`
cl hello.c /Fehello.exe

// Compile with maximum warnings and debug
cl /W4 /WX /Zi hello.c /Fehello_debug.exe

// Compile with optimization (`/O2`) and C17 standard
cl /O2 /std:c17 programa.c /Feprograma_otimizado.exe

// Link with Windows libraries (e.g., `user32.lib`)
cl winapp.c /link user32.lib /Fewinapp.exe

// Compile multiple files
cl /c arquivo1.c      # Generates arquivo1.obj
cl /c arquivo2.c      # Generates arquivo2.obj
cl arquivo1.obj arquivo2.obj /Feprograma.exe

Windows SDK

• Windows SDK .

What it includes

• Headers and Libraries :

  • Header files ( .h ) and linking libraries ( .lib ) to access Windows APIs.

  • Examples:

    • Win32 API : To create windows, manage files, etc.

    • DirectX : For graphics and game development.

    • GDI/GDI+ : For 2D graphics.

    • COM (Component Object Model) : For reusable components.

• Compilers :

  • Includes MSVC (Microsoft Visual C++) , used to compile native Windows code.

• Debuggers and Tools :

  • Tools such as WinDbg  for advanced debugging.

• Resource Viewers :

  • Tools to create and edit resource files (.rc), like icons, menus, and strings.

• Windows App Certification Kit :

  • Used to validate apps against Microsoft Store guidelines.

• Command-Line Tools :

  • Includes utilities like:

    • rc.exe : Resource file compiler.

    • mt.exe : Manifest tool.

    • signtool.exe : Binary signing tool.

• ARM64 Support :

  • Headers and libraries to compile apps for ARM devices on Windows.

QBE

• QBE .

  • "QBE is a compiler backend that aims to provide 70% of the performance of industrial optimizing compilers in 10% of the code."

  • "The size limit constrains QBE to focus on the essential and prevents embarking on a never-ending path of diminishing returns."

• QBE Demo .

Opinions

• Ginger Bill:

  • On Windows, and it's actually awful.

  • Worse than LLVM.

  • You have to generate a textual IR that you then pass to its library for it to be consumed.

  • And mainly because you cannot use it as a library whatsoever. It's designed not to be used as a library.

  • QBE is a no-go.

  • I've considered before, and no.