From 0583a84598a002ea99247506d41b3e8b302b2437 Mon Sep 17 00:00:00 2001
From: Abhinav Singh <73834077+abhinavsns@users.noreply.github.com>
Date: Fri, 18 Jul 2025 14:46:05 -0400
Subject: [PATCH] open-mpi: force build with brewed GCC
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Set ENV["CC"] and ENV["CXX"] to the Homebrew GCC shims
(gcc-<major>, g++-<major>) so that Open MPI always compiles
with the brewed GNU toolchain rather than Apple’s Clang.

This prevents breakage of GCC’s fixed headers on Xcode/Clang
upgrades and ensures ABI consistency for downstream MPI-using
formulae (e.g. PETSc, Trilinos) that rely on gfortran and MPI
wrappers. Bump revision to rebuild bottles under the new settings.
---
 Formula/o/open-mpi.rb | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Formula/o/open-mpi.rb b/Formula/o/open-mpi.rb
index 5c52a5d7a8592..db882299749a3 100644
--- a/Formula/o/open-mpi.rb
+++ b/Formula/o/open-mpi.rb
@@ -29,6 +29,7 @@ class OpenMpi < Formula
   end
 
   depends_on "gcc" # for gfortran
+  fails_with :clang
   depends_on "hwloc"
   depends_on "libevent"
   depends_on "pmix"
@@ -50,8 +51,8 @@ def install
       ompi/tools/ompi_info/param.c
       oshmem/tools/oshmem_info/param.c
     ]
-    cxx = OS.linux? ? "g++" : ENV.cxx
-    cc = OS.linux? ? "gcc" : ENV.cc
+    cxx = ENV.cxx
+    cc = ENV.cc
     inreplace inreplace_files, "OMPI_CXX_ABSOLUTE", "\"#{cxx}\""
     inreplace inreplace_files, "OPAL_CC_ABSOLUTE", "\"#{cc}\""
     inreplace "3rd-party/prrte/src/tools/prte_info/param.c", "PRTE_CC_ABSOLUTE", "\"#{cc}\""
@@ -74,6 +75,7 @@ def install
 
     system "./configure", *args, *std_configure_args
     system "make", "all"
+
     system "make", "check"
     system "make", "install"