Compile bug: Linker crash with tagged pointer truncation on Android 15 (Termux)

**Note: This issue was copied from [https://github.com/ggml-org/llama.cpp/issues/16658](https://github.com/ggml-org/llama.cpp/issues/16658)**

**Original Author:** @DevGitPit
**Original Issue Number:** #16658
**Created:** 2025-10-19T00:26:08Z

---

### Git commit

ee09828cb057460b369576410601a3a09279e23c

### Operating systems

Other? (Please let us know in description)

### GGML backends

CPU

### Problem description & steps to reproduce

Asked AI to prep this-

# Bug Report: Linker Crash with Tagged Pointer Truncation on Android 15 (Termux/aarch64)

## Summary
Building llama.cpp natively on Android 15 in Termux fails during the linking stage of certain binaries (`llama-quantize`, test binaries) with a linker crash related to tagged pointer truncation. The error only affects specific targets while others (`llama-cli`, `llama-server`) link successfully.

## Error Message
```
Pointer tag for 0x652760ba5e was truncated, see 'https://source.android.com/devices/tech/debug/tagged-pointers'.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
c++: error: unable to execute command: Aborted
c++: error: linker command failed due to signal (use -v to see invocation)
make[2]: *** [tools/quantize/CMakeFiles/llama-quantize.dir/build.make:108: bin/llama-quantize] Error 1
```

## Environment

### Device Information
- **Device**: realme RMX3853
- **Android Version**: 15
- **Kernel**: `6.1.118-android14-11-o-g8c6105bdb579 #1 SMP PREEMPT`
- **Architecture**: aarch64 (arm64-v8a only)

### CPU Features
```
fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm lrcpc dcpop asimddp
```

### Termux Information
- **Termux Version**: 0.118.3
- **APK Release**: F_DROID
- **Package Manager**: apt
- **Build System**: cmake
- **Compiler**: Clang 21.1.3

### llama.cpp Information
- **Version**: 0.9.4
- **Commit**: ee09828c

## Steps to Reproduce

### 1. Setup Termux Environment
```bash
pkg update && pkg upgrade
pkg install git cmake clang ccache
```

### 2. Clone Repository
```bash
git clone https://github.com/ggml-org/llama.cpp
cd llama.cpp
```

### 3. Build with Default Configuration
```bash
cmake -B build -DBUILD_SHARED_LIBS=OFF
cmake --build build --config Release -j $(nproc)
```

### 4. Observe Failure
Build progresses to approximately 94% completion, successfully compiling all source files. The failure occurs during the linking stage of `llama-quantize`:

```
[ 94%] Linking CXX executable ../../bin/llama-quantize
Pointer tag for 0x652760ba5e was truncated
c++: error: unable to execute command: Aborted
c++: error: linker command failed due to signal (use -v to see invocation)
```

## Build Configuration Details

### CMake Configuration Output (relevant sections)
```
-- CMAKE_SYSTEM_PROCESSOR: aarch64
-- GGML_SYSTEM_ARCH: ARM
-- Found OpenMP_C: -fopenmp=libomp (found version "5.1")
-- Found OpenMP_CXX: -fopenmp=libomp (found version "5.1")
-- ARM detected
-- ARM -mcpu not found, -mcpu=native will be used
-- Performing Test GGML_MACHINE_SUPPORTS_dotprod - Success
-- Performing Test GGML_MACHINE_SUPPORTS_i8mm - Failed
-- Performing Test GGML_MACHINE_SUPPORTS_noi8mm - Success
-- Performing Test GGML_MACHINE_SUPPORTS_sve - Failed
-- Performing Test GGML_MACHINE_SUPPORTS_nosve - Success
-- Performing Test GGML_MACHINE_SUPPORTS_sme - Failed
-- Performing Test GGML_MACHINE_SUPPORTS_nosme - Success
-- ARM feature DOTPROD enabled
-- ARM feature FMA enabled
-- ARM feature FP16_VECTOR_ARITHMETIC enabled
-- Adding CPU backend variant ggml-cpu: -mcpu=native+dotprod+noi8mm+nosve+nosme
```

### Compiler Flags Used
- Default cmake `RelWithDebInfo` build type
- `-mcpu=native+dotprod+noi8mm+nosve+nosme` (auto-detected)

## Observations

### Pattern of Failures
1. ✅ **Successful**: Compilation of all `.c` and `.cpp` files
2. ✅ **Successful**: Linking of simpler binaries:
   - `llama-cli`
   - `llama-server` 
   - `llama-simple`
   - `llama-embedding`
   - Most example binaries
3. ❌ **Failed**: Linking of specific binaries:
   - `llama-quantize` (consistently fails)
   - `test-grammar-parser` (when building with tests enabled)
   - Other test binaries (intermittent)

### Timing
- Failure occurs at ~94-96% build completion
- Only happens during the linking phase, never during compilation
- Appears to be related to binary size or complexity

### Tagged Pointers Context
Android 15 implements [Memory Tagging Extension (MTE)](https://source.android.com/devices/tech/debug/tagged-pointers) for enhanced memory safety. This feature uses the top byte of 64-bit pointers for tagging, which may cause compatibility issues with certain linker operations.

## Attempted Workarounds

### ✅ Successful Workaround #1: Build Only Required Targets
```bash
cmake -B build -DBUILD_SHARED_LIBS=OFF
cmake --build build --target llama-cli llama-server -j $(nproc)
```
**Result**: Successfully builds `llama-cli` and `llama-server` without errors.

### ✅ Successful Workaround #2: Disable Tools and Tests
```bash
cmake -B build \
  -DBUILD_SHARED_LIBS=OFF \
  -DLLAMA_BUILD_TOOLS=OFF \
  -DLLAMA_BUILD_TESTS=OFF
  
cmake --build build --config Release -j $(nproc)
```
**Result**: Successfully builds core binaries and examples.

### ✅ Successful Workaround #3: Manual Optimization Flags
```bash
cmake -B build \
  -DBUILD_SHARED_LIBS=OFF \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_C_FLAGS="-O3 -march=armv8.2-a+fp16+dotprod" \
  -DCMAKE_CXX_FLAGS="-O3 -march=armv8.2-a+fp16+dotprod" \
  -DGGML_NATIVE=OFF \
  -DLLAMA_CURL=OFF

cmake --build build --target llama-cli llama-server -j $(nproc)
```
**Result**: Successfully builds with full optimizations and avoids linker crash.

### ❌ Unsuccessful: Building All Targets
Any attempt to build `llama-quantize` or test binaries results in the linker crash.

## Performance Note

Binaries built with the manual optimization flags (Workaround #3) show **significantly better performance** than those built with default settings:
- Manual flags: Proper use of NEON, FMA, FP16, DOTPROD optimizations
- Better vectorization and aggressive compiler optimizations from `-O3`

## Additional Context

### Comparison with Other Android Versions
- **Android 12** (tested on separate device): Same build configuration works without issues
- **Android 14**: Unknown (not tested)
- **Android 15**: Consistent linker crashes as described

### Suspected Root Cause
This appears to be an interaction between:
1. Clang 21.x linker (LLD)
2. Android 15's Memory Tagging Extension
3. Binary size/complexity thresholds
4. Possibly related to LLVM's handling of tagged pointers in the linker

The selective nature of failures (simple binaries succeed, complex ones fail) suggests a threshold effect rather than a fundamental incompatibility.

## Requests for Assistance

1. **Is this a known issue** with Clang 21.x on Android 15?
2. **Should this be reported** to LLVM's issue tracker as well?
3. **Are there linker flags** that could disable memory tagging checks during linking?
4. **Can the build system** be modified to handle this more gracefully (e.g., detect Android 15 and apply workarounds)?

## Suggested Solutions

### Short-term (for users)
- Use targeted builds: `cmake --build build --target llama-cli llama-server`
- Apply manual optimization flags as shown in Workaround #3

### Long-term (for llama.cpp)
- Detect Android 15 and automatically disable problematic build targets
- Add documentation about this issue for Termux/Android 15 users
- Investigate linker flags that might resolve the tagged pointer issue
- Consider adding a build option like `-DANDROID15_WORKAROUND=ON`

## System Information Dump

<details>
<summary>Full Termux System Info</summary>

```
Termux Variables:
TERMUX_API_VERSION=0.53.0
TERMUX_APK_RELEASE=F_DROID
TERMUX_APP_PACKAGE_MANAGER=apt
TERMUX_APP_PID=1109
TERMUX_IS_DEBUGGABLE_BUILD=0
TERMUX_MAIN_PACKAGE_FORMAT=debian
TERMUX_VERSION=0.118.3
TERMUX__HOME=/data/data/com.termux/files/home
TERMUX__PREFIX=/data/data/com.termux/files/usr

Packages CPU architecture:
aarch64

Subscribed repositories:
deb https://termux.danyael.xyz/termux/termux-main stable main
deb https://termux.danyael.xyz/termux/termux-x11 x11 main
deb https://tur.kcubeterm.com tur-packages tur tur-on-device tur-continuous

Kernel build information:
Linux localhost 6.1.118-android14-11-o-g8c6105bdb579 #1 SMP PREEMPT Fri Aug 29 14:30:37 UTC 2025 aarch64 Android

Device: realme RMX3853
Android version: 15
Supported ABIs: arm64-v8a (64-bit only)
```
</details>

---

**Note**: The workarounds allow successful builds of essential binaries, so this issue does not block usage of llama.cpp on Android 15. However, it does prevent building the complete toolset and may indicate a broader compatibility concern with Android 15's memory tagging feature.

### First Bad Commit

_No response_

### Compile command

```shell
cmake -B build -DBUILD_SHARED_LIBS=OFF
cmake --build build --config Release -j $(nproc)
```

### Relevant log output

```shell
---above--
```

Compile bug: Linker crash with tagged pointer truncation on Android 15 (Termux) #49

Description

Git commit

Operating systems

GGML backends

Problem description & steps to reproduce

Bug Report: Linker Crash with Tagged Pointer Truncation on Android 15 (Termux/aarch64)

Summary

Error Message

Environment

Device Information

CPU Features

Termux Information

llama.cpp Information

Steps to Reproduce

1. Setup Termux Environment

2. Clone Repository

3. Build with Default Configuration

4. Observe Failure

Build Configuration Details

CMake Configuration Output (relevant sections)

Compiler Flags Used

Observations

Pattern of Failures

Timing

Tagged Pointers Context

Attempted Workarounds

✅ Successful Workaround #1: Build Only Required Targets

✅ Successful Workaround #2: Disable Tools and Tests

✅ Successful Workaround #3: Manual Optimization Flags

❌ Unsuccessful: Building All Targets

Performance Note

Additional Context

Comparison with Other Android Versions

Suspected Root Cause

Requests for Assistance

Suggested Solutions

Short-term (for users)

Long-term (for llama.cpp)

System Information Dump

First Bad Commit

Compile command

Relevant log output

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions