# Version 12: compile from C/C++

[Blog](https://asm-editor.specy.app/blog.md)

Web page: https://asm-editor.specy.app/blog/posts/version-12

Published 2026-10-05. Tags: [release](https://asm-editor.specy.app/blog/tags/release.md), [c-cpp](https://asm-editor.specy.app/blog/tags/c-cpp.md)

> Version 12.0.0 adds C/C++ compilation, source-to-assembly highlighting, source breakpoints, and libraries for compiled programs.

## Compile C and C++ to assembly

Version 12.0.0 adds C and C++ compilation to **MIPS**, **RISC-V** (32-bit and 64-bit), and **x86-64** assembly. You can inspect the compiler's output and run it in the simulator. MIPS and RISC-V offer **Clang** and **GCC**. x86-64 uses GCC.

Add a `.c` or `.cpp` File in a supported Target's Project and open it in the editor. Choose a compiler and optimization level beside **Compile**. Compilation opens the Generated assembly alongside the source. **Build** prepares it for the simulator, then **Run** executes it.

Compilation goes through [Compiler Explorer](https://godbolt.org/) and needs an internet connection. It sends your selected source, local headers, and the supplied library headers to that service. The compiled program runs in your browser. After editing the source or a header, Compile again to update the assembly.

## Follow source lines into assembly

C/C++ lines now share colors with the assembly instructions they produced, with connections between the two editors. Selecting a line highlights its instructions. Here, `total += n` becomes two loads, an addition, and a store in RISC-V. You can trace loops, branches, and function calls from familiar C into assembly.

![The selected C statement total += n connected to its generated RISC-V loads, addition, and store.](https://asm-editor.specy.app/images/blog/version-12/source-and-assembly.webp)

The optimization choices run from **-O0** through **-O3**, plus **-Os** for size. Start at -O0 to follow the source closely, then recompile at -O2 to see how the compiler rearranges or removes work. A teacher can use the same source to compare compilers or optimization levels during a lesson.

## Debug with the C/C++ source visible

Breakpoints can now be set in the C/C++ source margin. **Run** pauses at the corresponding instructions, and **Step** and **Undo** keep the current source line highlighted as you move through the assembly. One C statement can take several steps. Watch the registers and memory to see how its result is calculated.

![A RISC-V Debug session paused at a breakpoint on total += n, with matching C and assembly highlights, registers, memory, and the first printed total.](https://asm-editor.specy.app/images/blog/version-12/source-breakpoint.webp)

## Use libraries from C and C++

MIPS and RISC-V programs now have a Runtime library with a subset of the C standard library. Include `<stdio.h>` for Terminal output with `printf` and input with `scanf`, or `<stdlib.h>` for memory allocation with `malloc` and `free`. String, file, and math functions are also provided. C++ has wrappers such as `<cstdio>` and `std::printf`, plus `new` and `delete`. `<iostream>` and containers such as `std::vector` are not supplied, and exceptions and RTTI are disabled. In this release, x86-64 compilation supports programs without standard-library calls.

The Environment library, `<sim.h>`, gives C and C++ access to the simulator's services through `sim_` functions: `sim_print_int` prints an integer, for example, and `sim_sleep` waits. On MIPS and RISC-V, `SIM_SCREEN` declares a pixel array for the Screen. Write colors made with `sim_rgb` into that array to draw pixels, then inspect the stores in the Generated assembly. On x86-64, `<sim.h>` exposes Linux system calls such as `sim_write`.

Here, two C loops fill the RISC-V Screen with a color gradient, and `sim_print_string` reports when drawing is complete.

![C source using sim.h and SIM_SCREEN beside its generated RISC-V assembly, with the color gradient drawn on the Screen and a completion message in the Terminal.](https://asm-editor.specy.app/images/blog/version-12/c-screen.webp)

For the step-by-step workflow, see [Compile C/C++ with ASM Editor](https://asm-editor.specy.app/blog/posts/c-cpp-to-assembly.md). The [MIPS](https://asm-editor.specy.app/documentation/mips/using-c.md) and [RISC-V](https://asm-editor.specy.app/documentation/risc-v/using-c.md) Documentation lists the supported library functions and simulator services.