[MacPorts] #74234: gmp @6.3.0_0+universal produces corrupted gmp.h (contains ar-archive bytes instead of C header), breaking mpfr configure

[MacPorts]

#74234: gmp @6.3.0_0+universal produces corrupted gmp.h (contains ar-archive bytes
instead of C header), breaking mpfr configure
-----------------------------------------------------+--------------------
 Reporter:  pleumann                                 |      Owner:  (none)
     Type:  defect                                   |     Status:  new
 Priority:  Normal                                   |  Milestone:
Component:  ports                                    |    Version:
 Keywords:  universal, gmp, mpfr, arm64, corruption  |       Port:  gmp
-----------------------------------------------------+--------------------
 (I wrote this ticket with Claude, which I also used for debugging the
 problem. I hope that's ok. If there are questions or you need more
 information, please don't hesitate to contact me.)

 Installing gmp with the +universal variant (pulled in as a dependency of
 gdb, which uses the muniversal PortGroup) reliably produces a corrupted
 /opt/local/include/gmp.h. Instead of valid C header content, the file
 contains the start of a Unix ar archive:

 {{{
 !<arch>
 #1/20           1784278209  0     0     100644  28        `
 __.SYMDEF SORTED

 }}}

 file identifies it as:
 {{{
 /opt/local/include/gmp.h: current ar archive random library
 }}}
 This looks like libgmp.a (or a .symdef archive member) being written to
 the gmp.h destination path during the universal build's merge/lipo step,
 instead of the actual header.
 As a result, any port depending on gmp's headers fails to configure. In my
 case, mpfr fails with:
 {{{
 /opt/local/include/gmp.h:1:1: error: expected identifier or '('
 /opt/local/include/gmp.h:2:3: error: invalid filename for line marker
 directive
 configure:19720: error: gmp.h can't be found, or is unusable.
 }}}
 Steps to reproduce:

 1) sudo port install gdb (or directly sudo port install gmp +universal)

 2) Confirm the corrupted header:
 {{{
    head -5 /opt/local/include/gmp.h
 }}}
 3) Attempt to build mpfr against it:
 {{{
    sudo port clean mpfr
    sudo port install mpfr +universal
 }}}
 → configure fails with gmp.h can't be found, or is unusable.

 What I've ruled out:

 - Reinstalling gmp from scratch (port -f uninstall + reinstall) reproduces
 the corruption every time the +universal variant is built; a plain
 arm64-only gmp build (when I could get one, before discovering gdb's
 muniversal PortGroup forces universal regardless of variants.conf)
 produced a clean header every time.
 - Full reinstall of Command Line Tools (sudo rm -rf
 /Library/Developer/CommandLineTools && sudo xcode-select --install) — no
 change, still corrupts.
 - Complete removal and fresh reinstall of MacPorts itself (removed
 /opt/local, LaunchDaemons, receipts, Tcl packages, then reinstalled from
 the official .pkg) — no change, still corrupts on the very first
 +universal gmp build.
 - Setting -universal in /opt/local/etc/macports/variants.conf has no
 effect here, because gdb's Portfile uses PortGroup muniversal 1.0, which
 forces universal builds of gdb and its key dependencies (including gmp)
 independent of the global variants file or the multiarch variant.

 Given it reproduces identically on a completely clean MacPorts install and
 a completely clean CLT install, this looks like a genuine bug in the
 universal build/merge logic for gmp on this platform, rather than local
 environment corruption.

 Environment:

 - macOS: Tahoe 26.5.2 (Build 25F84)
 - Architecture: arm64 (Apple Silicon)
 - MacPorts: [paste output of `port version`]
 - Xcode CLT: Apple clang version 21.0.0 (clang-2100.1.1.101), freshly
 reinstalled
 - gmp port version: 6.3.0_0+universal
 - mpfr port version: 4.2.2_0

 port info --variants gmp returns:

 variants: native, universal

-- 
Ticket URL: <https://trac.macports.org/ticket/74234>
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