Xcode9下iOS Objective-C项目Lua库system函数不可用问题求助

Hey there, let's work through this issue. The system() function was restricted in iOS 11 and later, which breaks the third-party Lua library that worked perfectly in Xcode 8/iOS 10. Here are practical solutions to get your project running again:

1. Replace system() with iOS-Allowed APIs in Lua's Source Code #

The root issue is that Lua's os.execute() (and related functions) rely on system() under the hood. You can modify the Lua library's source to use posix_spawn—a supported alternative for spawning processes on iOS.

Step-by-Step: #

• Locate the file mentioned in the error: ioslib.c (or sometimes loslib.c in standard Lua distributions)
• Find the function that calls system()—usually the implementation of os_execute
• Replace the system() call with a custom implementation using posix_spawn

Here's a sample replacement function you can use:

#include <spawn.h>
#include <sys/wait.h>
#include <errno.h>

int custom_system(const char *command) {
    pid_t processId;
    char *arguments[] = {"/bin/sh", "-c", (char *)command, NULL};
    int exitStatus;

    // Spawn the shell process to execute the command
    int spawnResult = posix_spawn(&processId, "/bin/sh", NULL, NULL, arguments, NULL);
    if (spawnResult != 0) {
        // Return error code if spawn fails
        return -1;
    }

    // Wait for the process to finish and get exit status
    waitpid(processId, &exitStatus, 0);
    return WEXITSTATUS(exitStatus);
}

Then update the original code where system() was called to use custom_system() instead. For example, if the original line was:

int result = system(cmd);

Change it to:

int result = custom_system(cmd);

2. Use a Pre-Adapted Lua Library #

If you don't want to modify source code yourself, look for a Lua distribution that's already patched for iOS 11+. Options include:

• LuaJIT: Check if the latest version has addressed this restriction (note: ensure compatibility with your Objective-C project)
• Community-maintained Lua forks for iOS that explicitly remove dependencies on system()

3. Disable Unused system()-Dependent Features #

If your project doesn't actually use Lua's command-execution functions (like os.execute), you can:

• Comment out the sections of ioslib.c that call system()
• Compile Lua with the OS module disabled (check the Lua build configuration flags to exclude this module)

Important Notes: #

• Keep iOS sandbox restrictions in mind: Even with posix_spawn, you can only execute system binaries within your app's sandbox and can't access restricted system resources.
• After modifying the Lua source, recompile the library for your Xcode project to apply the changes.

内容的提问来源于stack exchange，提问作者Harry Boy