Incompatible function pointer types assigning to 'Function *' at readline module

[corona10]

At macOS 12.5.1 with Apple clang version 14.0.0 (clang-1400.0.29.202)

./Modules/readline.c:1252:21: warning: incompatible function pointer types assigning to 'Function *' (aka 'int (*)(const char *, int)') from 'int (void)' [-Wincompatible-function-pointer-types]
    rl_startup_hook = on_startup_hook;
                    ^ ~~~~~~~~~~~~~~~
./Modules/readline.c:1254:23: warning: incompatible function pointer types assigning to 'Function *' (aka 'int (*)(const char *, int)') from 'int (void)' [-Wincompatible-function-pointer-types]
    rl_pre_input_hook = on_pre_input_hook;

Linked PRs

• [WIP] gh-105323: Suppress function pointer warning by type casting #106284
• gh-105323: Add special workround for macOS default editline #108633
• gh-105323: Update readline module to detect apple editline variant #108665
• gh-105323: Remove WITH_APPLE_EDITLINE to use the same declaration for all editline #112513

[corona10]

Header from apple Xcode.

/* typedefs */
typedef int	  Function(const char *, int);
typedef void	  VFunction(void);
typedef void	  VCPFunction(char *);
typedef char	 *CPFunction(const char *, int);
typedef char	**CPPFunction(const char *, int, int);
typedef char     *rl_compentry_func_t(const char *, int);
typedef int	  rl_command_func_t(int, int);

[erlend-aasland]

@corona10, did you get any further with this? I'm getting annoyed at these warnings, myself :)

[corona10]

@erlend-aasland I will try to solve this issue at this weekend ;)

[corona10]

@ned-deily cc @erlend-aasland

Hi Ned,
AFAIK, Apple uses a different readline implementation from GNU and I checked API signatures were the same across versions.
https://github.com/phracker/MacOSX-SDKs
So we can easily solve this issue by using a conditional compile approach.

But if we have to care about linking with the GNU version on the macOS, the problem will be more difficult.
So we need to know that we should care or not.
https://stackoverflow.com/questions/7214374/how-do-i-link-against-the-gnu-readline-library-rather-than-libedit-in-macosx

[erlend-aasland]

But if we have to care about linking with the GNU version on the macOS, the problem will be more difficult.

You can use the preprocessor define WITH_EDITLINE to check if we're compiling with editline or readline.

[corona10]

You can use the preprocessor define WITH_EDITLINE to check if we're compiling with editline or readline.

Wow, That's good! I will prepare the patch by this weekend :)

[erlend-aasland]

If you grep for READLINE in configure.ac, you'll find that the dependency resolver for readline is more complex than that for other extension modules with third party dependencies. See also the WITH_EDITLINE conditional at the top of Modules/readline.c :)

[erlend-aasland]

See discussion on #108588