CONFIGURE:
sh configure \
--openjdk-target=aarch64-macos-ios \
--with-build-jdk=/pt/jdk-23.jdk/Contents/Home

Make sure to have CUPS installed on the referred path!

ISSUE:
configure: error: unsupported operating system ios
/Users/johan/openjdk/github/jdk/build/.configure-support/generated-configure.sh: line 84: 5: Bad file descriptor

SOLUTION:
add ios in platform.m4:
diff --git a/make/autoconf/platform.m4 b/make/autoconf/platform.m4
index 6aaf3b87f8d..6d49d6936ef 100644
--- a/make/autoconf/platform.m4
+++ b/make/autoconf/platform.m4
@@ -202,6 +202,10 @@ AC_DEFUN([PLATFORM_EXTRACT_VARS_FROM_OS],
       VAR_OS=android
       VAR_OS_TYPE=unix
       ;;
+    *ios*)
+      VAR_OS=ios
+      VAR_OS_TYPE=unix
+      ;;
     *linux*)
       VAR_OS=linux
       VAR_OS_TYPE=unix

ISSUE:
checking for fontconfig/fontconfig.h... no
configure: error: Could not find fontconfig!  

SOLUTION:
don't use fontconfig in libraries.m4
diff --git a/make/autoconf/libraries.m4 b/make/autoconf/libraries.m4
index d8c65109f67..2d255ec664a 100644
--- a/make/autoconf/libraries.m4
+++ b/make/autoconf/libraries.m4
@@ -52,7 +52,7 @@ AC_DEFUN_ONCE([LIB_DETERMINE_DEPENDENCIES],
   fi
 
   # Check if fontconfig is needed
-  if test "x$OPENJDK_TARGET_OS" = xwindows || test "x$OPENJDK_TARGET_OS" = xmacosx; then
+  if test "x$OPENJDK_TARGET_OS" = xwindows || test "x$OPENJDK_TARGET_OS" = xmacosx || test "x$OPENJDK_TARGET_OS" = xios; then
     # No fontconfig support on windows or macosx
     NEEDS_LIB_FONTCONFIG=false
   else

ISSUE:
configure: error: Could not find freetype! You might be able to fix this by running 'brew install freetype'. 

SOLUTION:
no freetype.
diff --git a/make/autoconf/lib-freetype.m4 b/make/autoconf/lib-freetype.m4
index d0859f36cc4..02185dedc1d 100644
--- a/make/autoconf/lib-freetype.m4
+++ b/make/autoconf/lib-freetype.m4
@@ -104,6 +104,7 @@ AC_DEFUN_ONCE([LIB_SETUP_FREETYPE],
   if test "x$OPENJDK_TARGET_OS" != "xwindows" && \
       test "x$OPENJDK_TARGET_OS" != "xmacosx" && \
       test "x$OPENJDK_TARGET_OS" != "xandroid" && \
+      test "x$OPENJDK_TARGET_OS" != "xios" && \
       test "x$OPENJDK_TARGET_OS" != "xaix"; then
     FREETYPE_TO_USE=system
   fi

ISSUE:
configure: error: Could not find X11 libraries. 

SOLUTION:
no X11
diff --git a/make/autoconf/libraries.m4 b/make/autoconf/libraries.m4
index d8c65109f67..779fc8f72e2 100644
--- a/make/autoconf/libraries.m4
+++ b/make/autoconf/libraries.m4
@@ -42,7 +42,7 @@ m4_include([lib-tests.m4])
 AC_DEFUN_ONCE([LIB_DETERMINE_DEPENDENCIES],
 [
   # Check if X11 is needed
-  if test "x$OPENJDK_TARGET_OS" = xwindows || test "x$OPENJDK_TARGET_OS" = xmacosx || test "x$OPENJDK_TARGET_OS" = xandroid; then
+  if test "x$OPENJDK_TARGET_OS" = xwindows || test "x$OPENJDK_TARGET_OS" = xmacosx || test "x$OPENJDK_TARGET_OS" = xandroid || test "x$OPENJDK_TARGET_OS" = xios; then
     # No X11 support on windows or macosx
     NEEDS_LIB_X11=false
   else

Configure then works, now make
cd build/ios-aarch64-minimal-release
make static-libs-image

add c1_globals_ios.hpp
add globals_ios.hpp

ISSUE:
In file included from /Users/johan/openjdk/github/jdk/src/hotspot/share/runtime/mutex.hpp:30:
/Users/johan/openjdk/github/jdk/src/hotspot/share/runtime/semaphore.hpp:34:11: fatal error: 'semaphore_ios.hpp' file not found

SOLUTION:
tell build system we're sort of LINUX, but also add __IOS__ to be
able to leverage Apple headers if we want to.
diff --git a/make/autoconf/flags-cflags.m4 b/make/autoconf/flags-cflags.m4
index e3aca36ad23..f846ab67ffb 100644
--- a/make/autoconf/flags-cflags.m4
+++ b/make/autoconf/flags-cflags.m4
@@ -468,6 +468,8 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_HELPER],
   elif test "x$OPENJDK_TARGET_OS" = xandroid; then
     CFLAGS_OS_DEF_JVM="-target aarch64-linux-android -DLINUX -D_ALLBSD_SOURCE -DANDROID"
     CFLAGS_OS_DEF_JDK="-target aarch64-linux-android -DLINUX -D__USE_BSD"
+  elif test "x$OPENJDK_TARGET_OS" = xios; then
+    CFLAGS_OS_DEF_JVM="-DLINUX -D__IOS__"
   fi

diff --git a/src/hotspot/share/utilities/globalDefinitions_gcc.hpp b/src/hotspot/share/utilities/globalDefinitions_gcc.hpp
index e5decbcd536..3160cf0f2e5 100644
--- a/src/hotspot/share/utilities/globalDefinitions_gcc.hpp
+++ b/src/hotspot/share/utilities/globalDefinitions_gcc.hpp
@@ -61,7 +61,7 @@
 
 #if defined(LINUX) || defined(_ALLBSD_SOURCE) || defined(_AIX)
 #include <signal.h>
-#ifndef __OpenBSD__
+#if !defined(__OpenBSD__) && !defined(__IOS__)
 #include <ucontext.h>
 #endif
 #ifdef __APPLE__

Also, runtime/os.hpp will check for BSD before it checks Linux.
Since we leverage a lot from Linux, we add an ios check before BSD
#elif defined(__IOS__)
  class Linux;


ISSUE:
Linking with ar @ fails, needs to provide list of objectfiles
diff --git a/make/common/native/Paths.gmk b/make/common/native/Paths.gmk
index e021a390289..bbe5a72e4cb 100644
--- a/make/common/native/Paths.gmk
+++ b/make/common/native/Paths.gmk
@@ -213,7 +213,7 @@ define SetupObjectFileList
 
     # If we are building static library, 'AR' on macosx/aix may not support @-file.
     ifeq ($$($1_TYPE), STATIC_LIBRARY)
-      ifeq ($(call isTargetOs, macosx aix), true)
+      ifeq ($(call isTargetOs, macosx ios aix), true)
         $1_LD_OBJ_ARG := `cat $$($1_OBJ_FILE_LIST)`
       endif
     endif


Java files

ISSUE:
No macosx classes included

SOLUTION:
diff --git a/make/common/Modules.gmk b/make/common/Modules.gmk
index 38ba9f0c559..5de04e8e903 100644
--- a/make/common/Modules.gmk
+++ b/make/common/Modules.gmk
@@ -91,6 +91,9 @@ endif
 ifeq ($(OPENJDK_TARGET_OS), android)
   SRC_SUBDIRS += linux/classes
 endif
+ifeq ($(OPENJDK_TARGET_OS), ios)
+  SRC_SUBDIRS += macosx/classes
+endif
 
 SRC_SUBDIRS += share/classes

ISSUE:
        int flags = followLinks ? 0 : CLONE_NOFOLLOW;

SOLUTION:
 this is generated from src/java.base/unix/classes/sun/nio/fs/UnixConstants.java.template with a check on __ALLBSD_SOURCE
diff --git a/make/autoconf/flags-cflags.m4 b/make/autoconf/flags-cflags.m4
index e3aca36ad23..8227d512e4e 100644
--- a/make/autoconf/flags-cflags.m4
+++ b/make/autoconf/flags-cflags.m4
@@ -468,6 +468,9 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_HELPER],
   elif test "x$OPENJDK_TARGET_OS" = xandroid; then
     CFLAGS_OS_DEF_JVM="-target aarch64-linux-android -DLINUX -D_ALLBSD_SOURCE -DANDROID"
     CFLAGS_OS_DEF_JDK="-target aarch64-linux-android -DLINUX -D__USE_BSD"
+  elif test "x$OPENJDK_TARGET_OS" = xios; then
+    CFLAGS_OS_DEF_JVM="-DLINUX -D__IOS__ " 
+    CFLAGS_OS_DEF_JDK="-D_ALLBSD_SOURCE"
   fi
 
   CFLAGS_OS_DEF_JDK="$CFLAGS_OS_DEF_JDK -D$OPENJDK_TARGET_OS_UPPERCASE"

ISSUE:
/Users/johan/openjdk/github/jdk/src/java.base/unix/native/libjava/TimeZone_md.c:500:14: error: call to undeclared function 'getPlatformTimeZoneID'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
        tz = getPlatformTimeZoneID();

SOLUTION:
diff --git a/src/java.base/unix/native/libjava/TimeZone_md.c b/src/java.base/unix/native/libjava/TimeZone_md.c
index 988c4bd2646..7cc978a40f9 100644
--- a/src/java.base/unix/native/libjava/TimeZone_md.c
+++ b/src/java.base/unix/native/libjava/TimeZone_md.c
@@ -63,7 +63,7 @@ static const char popularZones[][4] = {"UTC", "GMT"};
 static const char *ETC_ENVIRONMENT_FILE = "/etc/environment";
 #endif
 
-#if defined(__linux__) || defined(MACOSX)
+#if defined(__linux__) || defined(MACOSX) || defined(__IOS__)
 

ISSUE:
* For target support_native_jdk.management_libmanagement_ext_static_OperatingSystemImpl.o:
/Users/johan/openjdk/github/jdk/src/jdk.management/unix/native/libmanagement_ext/OperatingSystemImpl.c:41:10: fatal error: 'sys/proc_info.h' file not found
#include <sys/proc_info.h>
         ^~~~~~~~~~~~~~~~~
SOLUTION: