# Compiling Ninja from Source on Android Bionic

## Problem

The `ninja` build tool is required for meson-based projects (like frida Python extension), but:
1. Termux apt repo does not include a `ninja` package
2. PyPI `ninja` wheels are compiled for glibc Linux, not Android Bionic libc — they fail with "required file not found" at runtime
3. Compiling ninja from source hits Android Bionic compatibility issues

## Solution

### 1. Download Source

```bash
curl -L -o ninja-src.tar.gz \
  "https://github.com/ninja-build/ninja/archive/refs/tags/v1.12.1.tar.gz"
tar -xzf ninja-src.tar.gz
cd ninja-1.12.1
```

### 2. Patch Android Bionic Compatibility

Bionic libc lacks `struct sysinfo` and `SI_LOAD_SHIFT` used in `src/util.cc` for load average calculation.

**Patch `src/util.cc`** around line 895:

Replace:
```cpp
#elif defined(__UCLIBC__) || (defined(__BIONIC__) && __ANDROID_API__ < 29)
double GetLoadAverage() {
  struct sysinfo si;
  if (sysinfo(&si) != 0)
    return -0.0f;
  return 1.0 / (1 << SI_LOAD_SHIFT) * si.loads[0];
}
```

With:
```cpp
#elif defined(__BIONIC__)
#include <sys/system_properties.h>
double GetLoadAverage() {
  return -0.0f;
}
```

This skips load average reporting on Android (not needed for build functionality).

### 3. Compile

```bash
python3 configure.py --bootstrap
```

### 4. Install

```bash
cp ninja /data/data/com.termux/files/usr/bin/ninja
ninja --version
# Output: 1.12.1
```

## Pitfalls

1. **Do NOT use PyPI ninja wheel on Android** — manylinux tag does not mean Bionic compatible
2. **The `sysinfo` error is a red herring** — it's not about missing headers, it's about Bionic not implementing this Linux-specific feature
3. **Patch must be applied before bootstrap** — the error appears during compilation, not configuration

## Related

- `frida-devkit-termux-compilation.md` — Full frida devkit compilation flow that requires ninja