Is the underlying BOOL type a bool on Apple silicon

[schell]

I was confused about this library's definition of BOOL until finding this comment on SO, which explains that BOOL is a C signed char on Darwin and a C bool on iOS. I think we need to also check the target_os to distinguish between aarch64-apple-darwin and aarch64-apple-ios, because I'm seeing odd errors when compiling bluster dfrankland/bluster#44 on my M1 laptop.

I will submit a patch if it ends up working.

[madsmtm]

I don't have an M1 myself, but cross-compiling the following code:

// test_bool.m
#import <objc/objc.h>

BOOL BOOL_VALUE = 256;
_Bool C99_BOOL_VALUE = 256;
signed char SIGNED_CHAR_VALUE = 256;

char* BOOL_ = @encode(BOOL);
char* C99_BOOL = @encode(_Bool);
char* SIGNED_CHAR = @encode(signed char);

With:

$ clang -emit-llvm -S -target arm64-apple-darwin test_bool.m

Yields:

// Snippet
@BOOL_VALUE = global i8 1, align 1
@C99_BOOL_VALUE = global i8 1, align 1
@SIGNED_CHAR_VALUE = global i8 0, align 1
@.str = private unnamed_addr constant [2 x i8] c"B\00", align 1
@BOOL_ = global i8* getelementptr inbounds ([2 x i8], [2 x i8]* @.str, i32 0, i32 0), align 8
@C99_BOOL = global i8* getelementptr inbounds ([2 x i8], [2 x i8]* @.str, i32 0, i32 0), align 8
@.str.1 = private unnamed_addr constant [2 x i8] c"c\00", align 1
@SIGNED_CHAR = global i8* getelementptr inbounds ([2 x i8], [2 x i8]* @.str.1, i32 0, i32 0), align 8

Which strongly suggests that BOOL acts the same way as C99 _Bool/bool.

[madsmtm]

I think the problem is in your usage of get_ivar and set_ivar; you're trying to cast a boolean as a pointer type, while what you should be doing is just to use the correct type in your instance variable to begin with:

delegate.add_ivar::<BOOL>(POWERED_ON_IVAR);
let powered_on = delegate.get_ivar::<BOOL>(POWERED_ON_IVAR);
delegate.set_ivar::<BOOL>(POWERED_ON_IVAR, YES);

[schell]

Thank you for your quick reply.

Is there another step you're taking to compile the above test? Maybe including some headers or something? When I try I get this error:

❯ clang -emit-llvm -S -target arm64-apple-darwin test_bool.m                                                                                                             (base) 
test_bool.m:2:1: error: unknown type name 'BOOL'
BOOL BOOL_VALUE = 256;
^
test_bool.m:4:33: warning: implicit conversion from 'int' to 'signed char' changes value from 256 to 0 [-Wconstant-conversion]
signed char SIGNED_CHAR_VALUE = 256;
            ~~~~~~~~~~~~~~~~~   ^~~
test_bool.m:6:23: error: unknown type name 'BOOL'
char* BOOL_ = @encode(BOOL);
                      ^
1 warning and 2 errors generated.

[madsmtm]

Ah yes, sorry, I forgot to add an #import <objc/objc.h>; I've updated my comment to reflect this

[schell]

I made your suggested changes to bluster and it seems to pass tests, so maybe that's all it was!

[schell]

Also it looks like the llvm output is in fact the same on my machine as what you posted. Thank you for the investigation!