os.execShellCmd won't compile on IOS

[alexjba]

Description

It can be reproduced when compiling this code using the IOS SDK.

import browsers

openDefaultBrowser("https://github.com/nim-lang/Nim/issues")

    nim c --noMain:on --app:staticlib -d:ios --os:ios

The issue I have here is that openDefaultBrowser will eventually call system imported from stdlib.h. This symbol has been deprecated on IOS and will fail with Use posix_spawn APIs or NSTask instead. (On iOS, process spawning is unavailable.)

Nim/lib/pure/os.nim

Lines 210 to 211 in a18dcca

	proc c_system(cmd: cstring): cint {.
	importc: "system", header: "<stdlib.h>".}

Nim Version

Nim Compiler Version 2.0.12 [MacOSX: arm64]
Compiled at 2025-02-26
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: ce7c6f4

Current Output

Build fails with:

Use posix_spawn APIs or NSTask instead. (On iOS, process spawning is unavailable.)

Expected Output

Build succeeded.
The default browser is opened when the code runs.

Known Workarounds

No response

Additional Information

No response

[ringabout]

Hello, do you happen to have some tips/workflows to test the program on macOS. I spent hours in vain to try to learn swift and xcode.

[alexjba]

Hello, do you happen to have some tips/workflows to test the program on macOS. I spent hours in vain to try to learn swift and xcode.

I'm using QT for the nim library wrapper. It will generate the Xcode project for you. No swift or Xcode necessary. I just hope the steps below to work out of the box for you.

Installing QT

pip3 install -U pip
pip3 install aqtinstall
aqt install-qt mac ios 5.15.2 -O ~/Qt
### OR if it fails for arm64
arch -x86_64 aqt install-qt mac ios 5.15.2 -O ~/Qt

export QTDIR=~/Qt/5.15.2/ios
export PATH=${QTDIR}/bin:$PATH

Creating a new project

# Browser.pro file
TEMPLATE = app

SOURCES += main.cpp
LIBS += -l<nim library>

// main.cpp
#include <stdlib.h>
#include <unistd.h>

extern "C" {
    void NimMain();
}

int main(int argc, char* argv[])
{
    NimMain();
    return 0;
}

Building and running

mkdir build
cd build
# Generate the Xcode project
qmake ../browser.pro -spec macx-ios-clang CONFIG+=debug CONFIG+=iphonesimulator

# Build the project
xcodebuild -configuration Release -target "Qt Preprocess" -sdk iphonesimulator -arch x86_64
xcodebuild -configuration Release -target "Browser" install -sdk iphonesimulator -arch x86_64

# Find a simulator device. Copy the device id. (Should be installed by xcode)
xcrun simctl list devices

export SIMULATOR_DEVICE_ID=<your device id from the list above>
# Boot the device
xcrun simctl boot $SIMULATOR_DEVICE_ID
# Open the simulator 
open -a Simulator --args -CurrentDeviceUDID $SIMULATOR_DEVICE_ID
# Install the app
xcrun simctl install $SIMULATOR_DEVICE_ID <path to .app file built above>

[Araq]

So is this even fixable if iOS doesn't support process creation?

[alexjba]

My understanding is that system should be replaceable with posix_spawn. And the posix_spawn seems to be available on IOS

int     posix_spawn(pid_t * __restrict, const char * __restrict,
    const posix_spawn_file_actions_t *,
    const posix_spawnattr_t * __restrict,
    char *const __argv[__restrict],
    char *const __envp[__restrict]) __API_AVAILABLE(macos(10.5), ios(2.0)) __API_UNAVAILABLE(watchos, tvos);

[Araq]

Ok. typical Apple nonsense as I can implement system via posix_spawn+waitpid...