Re: [PATCH] Fix PR ada/111909 On Darwin, determine filesystem case sensitivity at runtime

[Iain Sandoe <iain@sandoe.co.uk>]

Hi Simon,

Thanks for persevering - I will keep the original patch, pending some chance to
fix the earlier OS issues.

I’ll check this on OS versions with older SDKs that do not have the TARGET_OS_XX
conditionals.

-----

One small nit below,

Iain

> On 21 Nov 2023, at 20:25, Simon Wright <simon@pushface.org> wrote:
> 
> On 21 Nov 2023, at 11:22, Iain Sandoe <iain@sandoe.co.uk> wrote:
>> 
>> Hello Simon, Arno,
>> 
>>> On 17 Nov 2023, at 13:43, Simon Wright <simon@pushface.org> wrote:
>>> 
>>>> 
>>>>> Apple’s naming is definitely confusing in this area!
>>>>> 
>>>>> In current SDKs, TARGET_OS_MAC means code is being generated for a Mac OS X variant, 
>>>>> which covers OSX, IOS, Watch … ; to determine which kind of device, you have to check the 
>>>>> specific define for that device - OSX corresponds to macOS, i.e. laptops, desktops.
>>>>> 
>>>>> In older SDKs (specifically Xcode 3, for macOS Leopard (darwin 9) as mentioned by Iain) 
>>>>> TARGET_OS_MAC means code is being generated for "Mac OS", i.e. laptops, desktops as 
>>>>> above; TARGET_OS_OSX is undefined (as are TARGET_OS_IOS etc).
>>>>> 
>>>>> If we are compiling for macOS, using a current macOS SDK, then TARGET_OS_MAC is
>>>>> set to 1 and TARGET_OS_OSX is set to 1. 
>>>>> 
>>>>> If we were compiling for iOS, using a current iOS SDK as supplied with current Xcode, then 
>>>>> TARGET_OS_MAC would be set to 1, TARGET_OS_OSX would be set to 0, and 
>>>>> TARGET_OS_IOS would be set to 1.
>>>> 
>>>> OK so then the following is sufficient for our needs:
>>>> 
>>>> #elif defined (__APPLE__)
>>>>     /* By default, macOS volumes are case-insensitive, iOS
>>>>        volumes are case-sensitive.  */
>>>> #if TARGET_OS_IOS
>>>>      file_names_case_sensitive_cache = 1;
>>>> #else
>>>>      file_names_case_sensitive_cache = 0;
>>>> #endif
>>>> #else /* Neither Windows nor Apple.  */
>>>>  file_names_case_sensitive_cache = 1;
>>>> #endif
>>>> 
>>>> We want the default to be 0, and we only care about setting it to 1 on iOS for recent
>>>> SDKs, the case of an old SDK and iOS isn't interesting at this stage, so it's fine if we set
>>>> the var to 0 in this scenario.
>>> 
>>> I can’t speak for Darwin maintainers, so I’ll leave it to Iain to comment on this suggestion.
>> 
>> * We are far away from having support for watchOS (32b Arm64) so I think that is a bridge
>> that can be crossed later.
>> 
>> * It seems to me that the proposed solution is better matched to the defaults on macOS/iOS.
>> 
>> * It would be better to have an automatic solution for folks (like me) who do use case-
>> sensitive file systems on macOS, but we do not have the resources right now to figure
>> out what is not working on the earlier systems.  I looked briefly, and found that the libcalls
>> are thin wrappers on a syscall, so that the different behaviours we are seeing on earlier
>> OS versions reflects the kernel’s handling of the provided path, rather than some improvement
>> in newer library functions.  That suggests to me that we will need to wrap the call in some more
>> complex logic to obtain the correct response.
>> 
>> So, I think that (with a test across the range of supported OS versions) the proposed
>> solution is an incremental improvement and we should take it.
>> 
>> When there’s a final proposed patch, I can add it into my testing across the systems.
>> 
>> Iain
> 
> Herewith my proposed patch (still in thread, though the subject of the thread isn’t still appropriate):
> 
> In gcc/ada/adaint.c(__gnat_get_file_names_case_sensitive), the current
> assumption for __APPLE__ is that file names are case-insensitive
> unless __arm__ or __arm64__ are defined, in which case file names are
> declared case-sensitive.
> 
> The associated comment is
>   "By default, we suppose filesystems aren't case sensitive on
>   Windows and Darwin (but they are on arm-darwin)."
> 
> This means that on aarch64-apple-darwin, file names are treated as
> case-sensitive, which is not the default case.
> 
> The true default position is that macOS file systems are
> case-insensitive, iOS file systems are case-sensitive.
> 
> Apple provide a header file <TargetConditionals.h> which permits a
> compile-time check for the compiler target (e.g. OSX vs IOS); if
> TARGET_OS_IOS is defined as 1, this is a build for iOS.
> 
> gcc/ada/Changelog:
> 
> 2023-11-21 Simon Wright <simon@pushface.org>
> 
>   * gcc/ada/adaint.c (__gnat_get_file_names_case_sensitive):
>   Split out the __APPLE__ check and remove the checks for __arm__,
>   __arm64__.
>   For Apple, file names are by default case-insensitive unless
>   TARGET_OS_IOS is set.
> 
> Signed-off-by: Simon Wright <simon@pushface.org>
> ---
>  gcc/ada/adaint.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/gcc/ada/adaint.c b/gcc/ada/adaint.c
> index bb4ed2607e5..0222791ed68 100644
> --- a/gcc/ada/adaint.c
> +++ b/gcc/ada/adaint.c
> @@ -84,7 +84,7 @@
>  #endif /* VxWorks */
>  
>  #if defined (__APPLE__)
> -#include <unistd.h>

If removing unistd.h is intentional (i.e. you determined that it’s no longer
needed for Darwin), then we should make that a separate patch.

> +#include <TargetConditionals.h>
>  #endif
>  
>  #if defined (__hpux__)
> @@ -613,11 +613,18 @@ __gnat_get_file_names_case_sensitive (void)
>        else
>  	{
>  	  /* By default, we suppose filesystems aren't case sensitive on
> -	     Windows and Darwin (but they are on arm-darwin).  */
> -#if defined (WINNT) || defined (__DJGPP__) \
> -  || (defined (__APPLE__) && !(defined (__arm__) || defined (__arm64__)))
> +	     Windows or DOS.  */
> +#if defined (WINNT) || defined (__DJGPP__)
>  	  file_names_case_sensitive_cache = 0;
> +#elif defined (__APPLE__)
> +	  /* By default, macOS volumes are case-insensitive, iOS
> +	     volumes are case-sensitive.  */
> +#if TARGET_OS_IOS
> +	  file_names_case_sensitive_cache = 1;
>  #else
> +	  file_names_case_sensitive_cache = 0;
> +#endif
> +#else /* Neither Windows nor Apple.  */
>  	  file_names_case_sensitive_cache = 1;
>  #endif
>  	}
> -- 
> 2.39.3 (Apple Git-145)
>