Fixed Darwin-specific undefined behavior in get_executable_directory()

[ink-splatters]

What

SIGABRT is received by the process on Darwin, due to

readlink("/proc/self/exe", filepath, 256);

failing to fill in the buffer (procfs does not exist on Darwin).

This causes undefined behavior in the subsequent code: null pointer dereference and attempt to write to invalid memory location (0x0000000000000001)

NOTE: though SIGABRT is received somewhat reproducibly,

man 2 readlink

says nothing about buffer contents in case of an error, which potentially may delay the failure beyond get_executable_directory(), causing unknown side effects.

Fix

using proc_pidpath() was implemented for Unix (primarily Darwin and other BSD systems).

Tests

the project was build using clang 17 from nixpkgs, on macOS running on Apple MacBook Air M1. The problem could not be reproduced anymore.

Click here for the details

$ arch
arm64

$ sw_vers

ProductName:		macOS
ProductVersion:		14.3.1
BuildVersion:		23D60

build.sh:

#!/usr/bin/env bash

set -e
set -o pipefail

CMAKE_SYSTEM_NAME=${CMAKE_SYSTEM_NAME:-Darwin}

CMAKE_EXE_LINKER_FLAGS=${CMAKE_EXE_LINKER_FLAGS:--fuse-ld=lld}
OpenMP_C_FLAGS=${OpenMP_C_FLAGS:--Xclang -fopenmp}
OpenMP_CXX_FLAGS=${OpenMP_CXX_FLAGS:--Xclang -fopenmp}
USE_STATIC_MOLTENVK=${USE_STATIC_MOLTENVK:-ON}
CMAKE_OSX_ARCHITECTURES=${CMAKE_OSX_ARCHITECTURES:-arm64}
CMAKE_CROSSCOMPILING=${CMAKE_CROSSCOMPILING:-ON}
CMAKE_SYSTEM_PROCESSOR=${CMAKE_SYSTEM_PROCESSOR:-arm64}

if [ "$1" = "--debug" ]; then
    # this is how I caught it with lldb
    CMAKE_C_FLAGS="-fno-limit-debug-info -g ${CMAKE_C_FLAGS}"
    CMAKE_CXX_FLAGS="-fno-limit-debug-info -g ${CMAKE_CXX_FLAGS}"
else
    CMAKE_C_FLAGS=${CMAKE_C_FLAGS:--O3}
    CMAKE_CXX_FLAGS=${CMAKE_CXX_FLAGS:--O3}
fi

mkdir -p build
cmake \
    -DCMAKE_SYSTEM_NAME="$CMAKE_SYSTEM_NAME" \
    -DCMAKE_C_FLAGS="$CMAKE_C_FLAGS" \
    -DCMAKE_CXX_FLAGS="$CMAKE_CXX_FLAGS" \
    -DCMAKE_EXE_LINKER_FLAGS="$CMAKE_EXE_LINKER_FLAGS" \
    -DOpenMP_C_FLAGS="$OpenMP_C_FLAGS" \
    -DOpenMP_CXX_FLAGS="$OpenMP_CXX_FLAGS" \
    -DUSE_STATIC_MOLTENVK="$USE_STATIC_MOLTENVK" \
    -DCMAKE_OSX_ARCHITECTURES="$CMAKE_OSX_ARCHITECTURES" \
    -DCMAKE_CROSSCOMPILING="$CMAKE_CROSSCOMPILING" \
    -DCMAKE_SYSTEM_PROCESSOR="$CMAKE_SYSTEM_PROCESSOR" \
    -G Ninja \
    -S src \
    -B build

cmake --build build

shell.nix:

with import <nixpkgs> { };
mkShell.override { inherit (llvmPackages_17) stdenv; } {
  buildInputs = with darwin.apple_sdk.frameworks;
    with llvmPackages_17; [
      openmp
      vulkan-headers
      vulkan-loader
      libcxx
      libcxxabi
      Metal
      QuartzCore
      CoreGraphics
      Cocoa
      IOKit
      IOSurface
      Foundation
    ];
  nativeBuildInputs = [ cmake ninja lld_17 glslang llvmPackages_17.bintools ];
}

$ nix-shell shell.nix --run './build.sh'

The resulted build unfortunately could not find valid GPU ( which is not related to this PR).

[NayamAmarshe]

We actually applied this fix a long time ago but never pushed the changes because my github was down for a whole month. Could you please check the changes and see if they're correct or need any correction?

Thank you very much for the PR and sorry for the delayed response.