Inconsistency in macos/macosx version CLI flag vs. availability attributes/macros

[h-vetinari]

The clang attribute reference says:

• macos:
  Apple’s macOS operating system. The minimum deployment target is specified by the -mmacosx-version-min=*version* command-line argument. macosx is supported for backward-compatibility reasons, but it is deprecated.

So we learn that the attribute should be spelled with macos, not macosx:

__attribute__((availability(macos,introduced=10.14)))

however, the CLI-flag as documented still uses the "x":

-mmacosx-version-min=*version*
       ^
       X

At the very least, this leads to confusion, as both forms are found in the current LLVM repo:

• search for -mmacosx-version-min
• search for -mmacos-version-min

I also believe it may lead to bugs, in the sense that -mmacosx-version-min=10.9 in newer clang ends up not setting MAC_OS_X_VERSION_MIN_REQUIRED or __MAC_OS_X_VERSION_MIN_REQUIRED?

I don't have a mac to test this hypothesis, but this is consistent with the failures I'm seeing.

[llvmbot]

@llvm/issue-subscribers-clang-driver

Author: None (h-vetinari)

The clang attribute [reference](https://clang.llvm.org/docs/AttributeReference.html#availability) says: > * `macos`: > Apple’s macOS operating system. The minimum deployment target is specified by the `-mmacosx-version-min=*version*` command-line argument. `macosx` is supported for backward-compatibility reasons, but it is deprecated.

So we learn that the attribute should be spelled with macos, not macosx:

__attribute__((availability(macos,introduced=10.14)))

however, the CLI-flag as documented still uses the "x":

-mmacosx-version-min=*version*
       ^
       X

At the very least, this leads to confusion, as both forms are found in the current LLVM repo:

• search for -mmacosx-version-min
• search for -mmacos-version-min

I also believe it may lead to bugs, in the sense that -mmacosx-version-min=10.9 in newer clang ends up not setting MAC_OS_X_VERSION_MIN_REQUIRED or __MAC_OS_X_VERSION_MIN_REQUIRED?

I don't have a mac to test this hypothesis, but this is consistent with the failures I'm seeing.

[h-vetinari]

CC @ldionne

[Xazax-hun]

The driver currently accepts both -mmacosx-version-min=10.9 and -mmacos-version-min=10.9, they are aliases:

llvm-project/clang/include/clang/Driver/Options.td

Line 4680 in f3afdc4

def : Joined<["-"], "mmacosx-version-min=">,

I tested them with the following small program and both seem to work as expected:

#include <AvailabilityMacros.h>
#include <iostream>

int main() {
  std::cout << MAC_OS_X_VERSION_MIN_REQUIRED << " "  << __MAC_OS_X_VERSION_MIN_REQUIRED << std::endl;
}

Is there any action item in this ticket? E.g., do we want to make one of the flags deprecated, potentially emitting a warning to migrate to another one? I am not sure how often are we doing that in Clang.

[h-vetinari]

Thanks for the response!

From my POV, the default CLI flag should match the naming in the availability macros, i.e. use macos not macosx. I don't care particularly if or how long the macosx spelling is kept around as an alias, but aside from the definition of the alias (and perhaps some docs about the preferred way going forward), all mentions of -mmacosx-version-min in the codebase should vanish IMO (and replaced by -mmacos-version-min).

[ldionne]

^ I agree. Basically, the action item in this ticket would be to make sure that the default flag is -mmacos-version-min and that the other one is an alias for it, and to update any references in the documentation that use -mmacosx-version-min to start steering users towards the preferred spelling.

[Xazax-hun]

I opened a PR to update the documentation and tests. I also realized scan-build did not properly handle the new spelling, so I also updated that.