From ea75839204a71ba390d7d0235be80bd96fdc51ab Mon Sep 17 00:00:00 2001
From: Andre Vehreschild <vehre@gcc.gnu.org>
Date: Wed, 18 Feb 2026 10:14:58 +0100
Subject: [PATCH] Fortran: Make caf_shmem build pthread presence aware.

On some system pthreads needs special treatment.  Use the present
AX_PTHREADS macro to figure what is needed.

libgfortran/ChangeLog:

	* Makefile.am: Only build caf_shmem when pthreads is available.
	* configure.ac: Check for pthreads availability and needed
	flags.

gcc/testsuite/ChangeLog:

	* gfortran.dg/coarray/caf.exp: Only add caf_shmem to tests when
	is build.
---
 gcc/testsuite/gfortran.dg/coarray/caf.exp | 18 +++++++++++++-----
 libgfortran/Makefile.am                   |  5 ++++-
 libgfortran/configure.ac                  | 10 ++++++++++
 3 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/gcc/testsuite/gfortran.dg/coarray/caf.exp b/gcc/testsuite/gfortran.dg/coarray/caf.exp
index 9cd99f8e0cb..02c3591f377 100644
--- a/gcc/testsuite/gfortran.dg/coarray/caf.exp
+++ b/gcc/testsuite/gfortran.dg/coarray/caf.exp
@@ -29,6 +29,7 @@
 # Load procedures from common libraries. 
 load_lib gfortran-dg.exp
 load_lib atomic-dg.exp
+load_lib target-libpath.exp
 
 # If a testcase doesn't have special options, use these.
 global DEFAULT_FFLAGS
@@ -48,6 +49,11 @@ global gfortran_test_path
 global gfortran_aux_module_flags
 set gfortran_test_path $srcdir/$subdir
 set gfortran_aux_module_flags $DEFAULT_FFLAGS
+global enable_caf_shmem
+set gccpath [get_multilibs]
+set shlib_ext [get_shlib_extension]
+set enable_caf_shmem [expr [file exists "${gccpath}/libgfortran/.libs/libcaf_shmem.a"] || \
+    [file exists "${gccpath}/libgfortran/.libs/libcaf_shmem.${shlib_ext}"] ]
 
 proc dg-compile-aux-modules { args } {
     global gfortran_test_path
@@ -110,11 +116,13 @@ foreach test [lsort [glob -nocomplain $srcdir/$subdir/*.\[fF\]{,90,95,03,08} ]]
 	cleanup-modules ""
     }
 
-    foreach flags $option_list {
-        verbose "Testing $nshort (libcaf_shmem), $flags" 1
-        set gfortran_aux_module_flags "-fcoarray=lib $flags -lcaf_shmem"
-        dg-test $test "-fcoarray=lib $flags -lcaf_shmem" {}
-        cleanup-modules ""
+    if "$enable_caf_shmem" {
+        foreach flags $option_list {
+            verbose "Testing $nshort (libcaf_shmem), $flags" 1
+            set gfortran_aux_module_flags "-fcoarray=lib $flags -lcaf_shmem"
+            dg-test $test "-fcoarray=lib $flags -lcaf_shmem" {}
+            cleanup-modules ""
+        }
     }
 }
 torture-finish
diff --git a/libgfortran/Makefile.am b/libgfortran/Makefile.am
index c5c0fa5717c..c57c5bec0e6 100644
--- a/libgfortran/Makefile.am
+++ b/libgfortran/Makefile.am
@@ -68,6 +68,8 @@ libcaf_single_la_LDFLAGS = -static
 libcaf_single_la_DEPENDENCIES = $(libcaf_shared_DEPS)
 libcaf_single_la_LINK = $(LINK) $(libcaf_single_la_LDFLAGS)
 
+if ENABLE_CAF_SHMEM
+libcaf_shmem_la_CFLAGS = $(CAF_SHMEM_CFLAGS)
 libcaf_shmem_la_SOURCES = $(libcaf_shared_SRCS) \
 	caf/shmem.c caf/shmem/alloc.c caf/shmem/allocator.c \
 	caf/shmem/collective_subroutine.c caf/shmem/counter_barrier.c \
@@ -80,7 +82,8 @@ libcaf_shmem_la_DEPENDENCIES = $(libcaf_shared_DEPS) caf/shmem/alloc.h \
 	caf/shmem/counter_barrier.h caf/shmem/hashmap.h \
 	caf/shmem/shared_memory.h caf/shmem/supervisor.h caf/shmem/sync.h \
 	caf/shmem/teams_mgmt.h caf/shmem/thread_support.h
-libcaf_shmem_la_LINK = $(LINK) $(libcaf_shmem_la_LDFLAGS)
+libcaf_shmem_la_LINK = $(LINK) $(libcaf_shmem_la_LDFLAGS) $(CAF_SHMEM_LIBS)
+endif
 
 if IEEE_SUPPORT
 fincludedir = $(libdir)/gcc/$(target_alias)/$(gcc_version)$(MULTISUBDIR)/finclude
diff --git a/libgfortran/configure.ac b/libgfortran/configure.ac
index b165dff1e05..fea8292225b 100644
--- a/libgfortran/configure.ac
+++ b/libgfortran/configure.ac
@@ -343,6 +343,16 @@ else
    freelocale uselocale strerror_l strtof128 strfromf128)
 fi
 
+# Check for existing and usable pthreads.
+AX_PTHREAD([
+  enable_caf_shmem=true
+  CAF_SHMEM_CFLAGS="$PTHREAD_CFLAGS"
+  CAF_SHMEM_LIBS="$PTHREAD_LIBS"
+  ], [
+  enable_caf_shmem=false
+  ])
+AM_CONDITIONAL([ENABLE_CAF_SHMEM], [test x$enable_caf_shmem = xtrue])
+
 # Check strerror_r, cannot be above as versions with two and three arguments exist
 LIBGFOR_CHECK_STRERROR_R