The commits from https://github.com/diml/ocaml/tree/fix-clang-build

patch.diff

From c83068bd7b95b3e29b2edc9410cea4b14625f3aa Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Wed, 12 Mar 2014 14:39:21 +0000
Subject: [PATCH] Do not pass -fno-defer-pop to clang

---
 configure | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/configure b/configure
index d45e88f..e5a0bf4 100755
--- a/configure
+++ b/configure
@@ -321,6 +321,17 @@ case "$bytecc,$target" in
     # Almost the same as NeXTStep
     bytecccompopts="-fno-defer-pop $gcc_warnings -DSHRINKED_GNUC"
     mathlib="";;
+  *clang,*-*-darwin*)
+    # -fno-defer-pop is not supported by clang, and make recent
+    # versions of clang to fail.
+    bytecccompopts="$gcc_warnings"
+    mathlib=""
+    mkexe="$mkexe -Wl,-no_compact_unwind"
+    # Tell gcc that we can use 32-bit code addresses for threaded code
+    # unless we are compiled for a shared library (-fPIC option)
+    echo "#ifndef __PIC__" >> m.h
+    echo "#  define ARCH_CODE32" >> m.h
+    echo "#endif" >> m.h;;
   *,*-*-darwin*)
     bytecccompopts="-fno-defer-pop $gcc_warnings"
     mathlib=""
-- 
1.8.4.2

From 73be7477f9b0f279fc2b20c7016dc95836b8c4b7 Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Wed, 12 Mar 2014 16:16:15 +0000
Subject: [PATCH] Check if gcc is an alias to clang

---
 configure | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/configure b/configure
index e5a0bf4..5f22143 100755
--- a/configure
+++ b/configure
@@ -321,19 +321,15 @@ case "$bytecc,$target" in
     # Almost the same as NeXTStep
     bytecccompopts="-fno-defer-pop $gcc_warnings -DSHRINKED_GNUC"
     mathlib="";;
-  *clang,*-*-darwin*)
-    # -fno-defer-pop is not supported by clang, and make recent
-    # versions of clang to fail.
-    bytecccompopts="$gcc_warnings"
-    mathlib=""
-    mkexe="$mkexe -Wl,-no_compact_unwind"
-    # Tell gcc that we can use 32-bit code addresses for threaded code
-    # unless we are compiled for a shared library (-fPIC option)
-    echo "#ifndef __PIC__" >> m.h
-    echo "#  define ARCH_CODE32" >> m.h
-    echo "#endif" >> m.h;;
   *,*-*-darwin*)
-    bytecccompopts="-fno-defer-pop $gcc_warnings"
+    # On recent version of OSX, gcc is a symlink to clang
+    if $bytecc --version | grep -q ^clang; then
+        # -fno-defer-pop is not supported by clang, and make recent
+        # versions of clang to fail
+        bytecccompopts="$gcc_warnings"
+    else
+        bytecccompopts="-fno-defer-pop $gcc_warnings"
+    fi
     mathlib=""
     mkexe="$mkexe -Wl,-no_compact_unwind"
     # Tell gcc that we can use 32-bit code addresses for threaded code
-- 
1.8.4.2

From f2fd13b96528323270c35c4a221032beb7c4e91f Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Wed, 12 Mar 2014 16:18:49 +0000
Subject: [PATCH] Relax the clang check

---
 configure | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/configure b/configure
index 5f22143..25d872b 100755
--- a/configure
+++ b/configure
@@ -323,7 +323,7 @@ case "$bytecc,$target" in
     mathlib="";;
   *,*-*-darwin*)
     # On recent version of OSX, gcc is a symlink to clang
-    if $bytecc --version | grep -q ^clang; then
+    if $bytecc --version | grep -q clang; then
         # -fno-defer-pop is not supported by clang, and make recent
         # versions of clang to fail
         bytecccompopts="$gcc_warnings"
-- 
1.8.4.2