iOS compiler stubs override environment-based minimum version specifications

[freakboy3742]

Bug report

Bug description:

Python includes shims for compiler tools on iOS to match GNU conventions for compiler names (e.g., arm64-apple-ios-clang) to avoid encoding a user-specific location to a compiler in sysconfig, and to avoid issues with UNIX build tools that expect CC/CXX to be single arguments without spaces.

Using this approach arm64-apple-ios-clang expands internal as xcrun --sdk iphoneos clang -target arm64-apple-ios-clang

Unfortunately, Apple has 3 ways to define a minimum iOS version, in order of priority:

1. the IPHONEOS_DEPLOYMENT_TARGET=12.0 environment variable
2. the -mios-min-version=12.0 command line argument
3. a version number encoded in a -target arm64-apple-ios12.0-simulator argument

If you specify all three options, (1) will be ignored, and (2) will raise a warning if the version it specifies doesn't match the version specified by (3).

The problem arises if you specify -target arm64-apple-ios-simulator- which is what the shim currently encodes.

If the -target doesn't specify a version, this is interpreted as "no min version". An explicitly provided -mios-version-min definition will override this minimum without warning; but any IPHONEOS_DEPLOYMENT_VERSION value will be ignored.

Thus, using the compiler shims in an environment where IPHONEOS_DEPLOYMENT_VERSION is defined will result in this value being ignored unless the minimum version is also passed in as a -mios-version-min argument.

CPython versions tested on:

3.13

Operating systems tested on:

Other

Linked PRs

• gh-133183: Include IPHONEOS_DEPLOYMENT_TARGET in iOS shim targets. #133184
• [3.13] gh-133183: Include IPHONEOS_DEPLOYMENT_TARGET in iOS shim targets. (GH-133184) #133234