====== 1.3 Emscripten SDK ======

Emscripten is a compiler that compiles C/C++ to WebAssembly (WASM).

----

===== What is Emscripten? =====

**Emscripten** translates:
  * C/C++ code → WebAssembly
  * System APIs → JavaScript equivalents
  * OpenGL → WebGL

<WRAP info>
**Why do we need Emscripten?**

For the WASM build of OpenSSL that runs in Blazor WebAssembly.
</WRAP>

----

===== Prerequisites =====

  * ☑ [[.:wsl-einrichten|WSL2 installed]]
  * ☑ Git available

----

===== Installation in WSL =====

==== Step 1: Open WSL ====

<code bash>
wsl
</code>

==== Step 2: Clone Emscripten SDK ====

<code bash>
# To the opt directory (system-wide)
cd /opt

# Clone as root
sudo git clone https://github.com/emscripten-core/emsdk.git
sudo chown -R $USER:$USER /opt/emsdk
</code>

Or in home directory (only for your user):

<code bash>
git clone https://github.com/emscripten-core/emsdk.git ~/emsdk
cd ~/emsdk
</code>

==== Step 3: Install latest version ====

<code bash>
cd /opt/emsdk   # or ~/emsdk

# Install latest stable version
./emsdk install latest

# Activate
./emsdk activate latest
</code>

==== Step 4: Set environment variables ====

**Temporary (this session only):**
<code bash>
source /opt/emsdk/emsdk_env.sh
</code>

**Permanent (in .bashrc):**
<code bash>
echo 'source /opt/emsdk/emsdk_env.sh' >> ~/.bashrc
</code>

----

===== Verification =====

<code bash>
# Emscripten Compiler
emcc --version
</code>

Expected output:
<code>
emcc (Emscripten gcc/clang-like replacement) 3.1.xx
</code>

<code bash>
# Additional tools
emar --version
emranlib --version
</code>

----

===== Quick Test =====

Create a test file:

<code bash>
cat > hello.c << 'EOF'
#include <stdio.h>

int main() {
    printf("Hello from WebAssembly!\n");
    return 0;
}
EOF
</code>

Compile to WASM:

<code bash>
emcc hello.c -o hello.js

# Run with Node.js
node hello.js
# Output: Hello from WebAssembly!
</code>

----

===== For OpenSSL Build =====

For the WASM build of OpenSSL, these Emscripten tools are used:

| Tool | Usage |
|------|-------|
| ''emcc'' | C compiler (replaces gcc) |
| ''emar'' | Archiver (replaces ar) |
| ''emranlib'' | Ranlib (replaces ranlib) |
| ''emconfigure'' | Wrapper for ./Configure |
| ''emmake'' | Wrapper for make |

**Example:**

<code bash>
# Instead of:
./Configure linux-x86_64
make

# With Emscripten:
emconfigure ./Configure linux-generic32
emmake make
</code>

----

===== Update Version =====

<code bash>
cd /opt/emsdk   # or ~/emsdk

# Fetch updates
git pull

# Install latest version
./emsdk install latest
./emsdk activate latest

# Reload environment
source ./emsdk_env.sh
</code>

----

===== Common Problems =====

==== "emcc: command not found" ====

Environment not loaded:

<code bash>
source /opt/emsdk/emsdk_env.sh
</code>

==== "Python not found" ====

Emscripten needs Python 3:

<code bash>
# Ubuntu
sudo apt install python3

# Fedora
sudo dnf install python3
</code>

==== Old version activated ====

<code bash>
# Check active version
emcc --version

# If outdated, reactivate
cd /opt/emsdk
./emsdk activate latest
source ./emsdk_env.sh
</code>

----

===== Continue to =====

  * [[.:build:wasm-blazor|WASM/Blazor Build]]
  * [[.:vorbereitung:start|Back to Preparation]]

----
//Wolfgang van der Stille @ EMSR DATA d.o.o. - Post-Quantum Cryptography Professional//