iOS 14.5 / Xcode 12.5 Build Issue: Semantic Issue (Comparison of distinct pointer types)

[roblabs]

There is a compiler error when building the scheme dynamic with Xcode.

Tested against:

• Version 12.5 (12E262) released on Apr 20, 2021
• Version 12.5 beta 3 (12E5244e) released on Mar 2, 2021.
• Version 12.5 beta 2 (12E5234g) released on Feb 16, 2021.
• Version 12.5 Beta (12E5220o) released on Feb 1, 2021.

This same file (NSExpression+MGLAdditions.mm) compiles fine with Xcode Version 12.4 (12D4e) & Xcode Version 11.7 (11E801a)

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Xcode reports Semantic Issue

Comparison of distinct pointer types ('NSString *' and 'Class')

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https://github.com/maptiler/maplibre-gl-native/blob/72692d6305bb4df1d64dab450e0d49e2c8d5c943/platform/ios/platform/darwin/src/NSExpression%2BMGLAdditions.mm#L1272

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Error in Xcode 12.5 Beta

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Other parameters of note:

• SDK iOS 14.5 (released as Beta on Feb 1, 2021)

[roblabs]

New type of error when attempting to build with Version 12.5 beta 3 (12E5244e) when testing with master: dba5d96

Cast to smaller integer type 'unsigned int' from 'MGLReachability *'

[roblabs]

This issue still exists & is a blocker for anyone intending to upgrade to Xcode 12.5 RC for MapLibre development. I recommend sticking with Xcode 11.7 or 12.4 to build MapLibre.

[roblabs]

If you are keen to upgrade to Xcode 12.5, you can help investigate or make a test case to ensure that the following is the right fix and/or a proper workaround.

//                           (NSString *) // Fixing the error by casting.  TODO verify it doesn't break something else
            } else if (op == (NSString *) [MGLColor class] && [function isEqualToString:@"colorWithRed:green:blue:alpha:"]) {

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Diff from within Xcode 12.5

[glyuck]

Regarding the error in MGLReachability.m and Cast to smaller integer type 'unsigned int' from 'MGLReachability *' warning:
I think we should replace

    NSString *description = [NSString stringWithFormat:@"<%@: %#x (%@)>",
                             NSStringFromClass([self class]), (unsigned int) self, [self currentReachabilityFlags]];

with

    NSString *description = [NSString stringWithFormat:@"<%@: %p (%@)>",
                             NSStringFromClass([self class]), (void *) self, [self currentReachabilityFlags]];

The first warning Comparison of distinct pointer types ('NSString *' and 'Class'):

} else if (op == [MGLColor class] && [function isEqualToString:@"colorWithRed:green:blue:alpha:"]) {

It looks like a bug in Mapbox source code to me: op == [MGLColor class] the left variable is NSString * and the right one is Class. I can't figure out how it supposed to work.
Probably it should be something like [op isEqualToString:NSStringFromClass([MGLColor class])]

[roblabs]

@glyuck — thanks for the contribution!

With this commit we now support Xcode 12.5 & Xcode 13-beta. And as a bonus MapLibre runs on the simulator on Apple Silicon with the latest Xcode release & beta.

Commit 19b86f7 has been tested on:

• both flavors of Big Sur (Intel & arm)
• a couple of Xcode versions that I had lying around

Xcode Version	c++ version	Catalina	Big Sur (Intel)	Big Sur (arm)
12.4 (12D4e)	12.0.0.12000032	✅Xcode 12.4 runs on Catalina & Big Sur	✅	Not tested
12.5.1 (12E507)	12.0.5.12050022	❌Xcode 12.5 requires Big Sur	✅	✅
13.0 (13A5192i)	13.0.0.13000025	❌Xcode 13-beta requires Big Sur	✅	✅

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macOS Version Info

uname -a

Catalina

Darwin catalina.local 19.6.0 Darwin Kernel Version 19.6.0: Tue Jun 22 19:49:55 PDT 2021; root:xnu-6153.141.35~1/RELEASE_X86_64 x86_64

Big Sur (Intel)

Darwin bigsur-intel.local 20.6.0 Darwin Kernel Version 20.6.0: Wed Jun 23 00:26:31 PDT 2021; root:xnu-7195.141.2~5/RELEASE_X86_64 x86_64

Big Sur (arm)

Darwin bigsur-arm.local 20.6.0 Darwin Kernel Version 20.6.0: Wed Jun 23 00:26:27 PDT 2021; root:xnu-7195.141.2~5/RELEASE_ARM64_T8101 arm64