Add iOS build support for USD Core

This PR adds **Core** iOS support to the OpenUSD project. This does not include Imaging, and any Imaging related components at this time. Imaging will be added in a follow up PR. MaterialX is also disabled as requested and the upgrade will be handled in a follow up PR.

It is a minimal version of PixarAnimationStudios#2455 against the latest `dev` branch.
Changes include:
* Using latest dev branch
* No imaging support. Will be added in a follow up PR.
* Makes use of CMake's inbuilt iOS support, negating the need for toolchain support
* Structures the code in such a way that we can add support for other iOS derived platforms+simulator in future PRs
* Swaps `ARCH_OS_IOS` with `ARCH_OS_IPHONE` to align with compiler directives. IPHONE refers to all derivative platforms, whereas iOS refers to only iPhone/iPad (Confusing but the case for historical reasons as [documented here](https://chaosinmotion.com/2021/08/02/things-to-remember-compiler-conditionals-for-macos-ios-etc/))
* TBB requires SDKROOT to be passed in or it can often go off and find some random compiler toolchain and fail.
* Add APPLE_EMBEDDED boolean to designate when using the CMake supported cross compilation targets. Added in Options.cmake so it can be used to configure defaults properly.

README.md

@@ -129,7 +129,7 @@ then build and install USD into `/path/to/my_usd_install_dir`.
 > python OpenUSD/build_scripts/build_usd.py /path/to/my_usd_install_dir
 ```
 
-##### MacOS:
+##### macOS:
 
 In a terminal, run `xcode-select` to ensure command line developer tools are
 installed. Then run the script.
@@ -141,6 +141,16 @@ then build and install USD into `/path/to/my_usd_install_dir`.
 > python OpenUSD/build_scripts/build_usd.py /path/to/my_usd_install_dir
 ```
 
+###### iOS
+
+When building from a macOS system, you can cross compile for iOS based platforms.
+
+iOS builds currently do not support Imaging.
+Additionally, they will not support Python bindings or command line tools.
+
+To build for iOS, add the `--build-target iOS` parameter.
+
+
 ##### Windows:
 
 Launch the "x64 Native Tools Command Prompt" for your version of Visual Studio

build_scripts/apple_utils.py

@@ -35,44 +35,47 @@
 import platform
 import shlex
 import subprocess
+import re
+from typing import Optional, List
 
 TARGET_NATIVE = "native"
 TARGET_X86 = "x86_64"
 TARGET_ARM64 = "arm64"
 TARGET_UNIVERSAL = "universal"
+TARGET_IOS = "ios"
+
+EMBEDDED_PLATFORMS = [TARGET_IOS]
 
 def GetBuildTargets():
     return [TARGET_NATIVE,
             TARGET_X86,
             TARGET_ARM64,
-            TARGET_UNIVERSAL]
+            TARGET_UNIVERSAL,
+            TARGET_IOS]
 
 def GetBuildTargetDefault():
-    return TARGET_NATIVE;
+    return TARGET_NATIVE
 
 def MacOS():
     return platform.system() == "Darwin"
 
 def GetLocale():
     return sys.stdout.encoding or locale.getdefaultlocale()[1] or "UTF-8"
 
-def GetCommandOutput(command):
+def GetCommandOutput(command, **kwargs):
     """Executes the specified command and returns output or None."""
     try:
-        return subprocess.check_output(
-            shlex.split(command),
-            stderr=subprocess.STDOUT).decode(GetLocale(), 'replace').strip()
-    except subprocess.CalledProcessError:
-        pass
-    return None
+        return subprocess.check_output(command, stderr=subprocess.STDOUT, **kwargs).decode(GetLocale(), 'replace').strip()
+    except:
+        return None
 
 def GetTargetArmArch():
     # Allows the arm architecture string to be overridden by
     # setting MACOS_ARM_ARCHITECTURE
     return os.environ.get('MACOS_ARM_ARCHITECTURE') or TARGET_ARM64
 
 def GetHostArch():
-    macArch = GetCommandOutput('arch').strip()
+    macArch = GetCommandOutput(["arch"])
     if macArch == "i386" or macArch == TARGET_X86:
         macArch = TARGET_X86
     else:
@@ -85,7 +88,7 @@ def GetTargetArch(context):
     else:
         if context.targetX86:
             macTargets = TARGET_X86
-        if context.targetARM64:
+        if context.targetARM64 or context.buildTarget in EMBEDDED_PLATFORMS:
             macTargets = GetTargetArmArch()
         if context.targetUniversal:
             macTargets = TARGET_X86 + ";" + GetTargetArmArch()
@@ -106,6 +109,8 @@ def GetTargetArchPair(context):
         primaryArch = TARGET_X86
     if context.targetARM64:
         primaryArch = GetTargetArmArch()
+    if context.targetIos:
+        primaryArch = TARGET_IOS
     if context.targetUniversal:
         primaryArch = GetHostArch()
         if (primaryArch == TARGET_X86):
@@ -118,18 +123,33 @@ def GetTargetArchPair(context):
 def SupportsMacOSUniversalBinaries():
     if not MacOS():
         return False
-    XcodeOutput = GetCommandOutput('/usr/bin/xcodebuild -version')
+    XcodeOutput = GetCommandOutput(["/usr/bin/xcodebuild", "-version"])
     XcodeFind = XcodeOutput.rfind('Xcode ', 0, len(XcodeOutput))
     XcodeVersion = XcodeOutput[XcodeFind:].split(' ')[1]
     return (XcodeVersion > '11.0')
 
+
+def GetSDKRoot(context) -> Optional[str]:
+    sdk = "macosx"
+    if context.buildTarget == TARGET_IOS:
+        sdk = "iphoneos"
+
+    for arg in (context.cmakeBuildArgs or '').split():
+        if "CMAKE_OSX_SYSROOT" in arg:
+            override = arg.split('=')[1].strip('"').strip()
+            if override:
+                sdk = override
+    return GetCommandOutput(["xcrun", "--sdk", sdk, "--show-sdk-path"])
+
+
 def SetTarget(context, targetName):
     context.targetNative = (targetName == TARGET_NATIVE)
     context.targetX86 = (targetName == TARGET_X86)
     context.targetARM64 = (targetName == GetTargetArmArch())
     context.targetUniversal = (targetName == TARGET_UNIVERSAL)
+    context.targetIos = (targetName == TARGET_IOS)
     if context.targetUniversal and not SupportsMacOSUniversalBinaries():
-        self.targetUniversal = False
+        context.targetUniversal = False
         raise ValueError(
                 "Universal binaries only supported in macOS 11.0 and later.")
 
@@ -150,26 +170,63 @@ def ExtractFilesRecursive(path, cond):
                 files.append(os.path.join(r, file))
     return files
 
-def CodesignFiles(files):
-    SDKVersion  = subprocess.check_output(
-        ['xcodebuild', '-version']).strip()[6:10]
-    codeSignIDs = subprocess.check_output(
-        ['security', 'find-identity', '-vp', 'codesigning'])
+def _GetCodeSignStringFromTerminal():
+    codeSignIDs = GetCommandOutput(['security', 'find-identity', '-vp', 'codesigning'])
+    return codeSignIDs
 
-    codeSignID = "-"
+def GetCodeSignID():
     if os.environ.get('CODE_SIGN_ID'):
-        codeSignID = os.environ.get('CODE_SIGN_ID')
-    elif float(SDKVersion) >= 11.0 and \
-                codeSignIDs.find(b'Apple Development') != -1:
-        codeSignID = "Apple Development"
-    elif codeSignIDs.find(b'Mac Developer') != -1:
-        codeSignID = "Mac Developer"
+        return os.environ.get('CODE_SIGN_ID')
+
+    codeSignIDs = _GetCodeSignStringFromTerminal()
+    if not codeSignIDs:
+        return "-"
+    for codeSignID in codeSignIDs.splitlines():
+        if "CSSMERR_TP_CERT_REVOKED" in codeSignID:
+            continue
+        if ")" not in codeSignID:
+            continue
+        codeSignID = codeSignID.split()[1]
+        break
+    else:
+        raise RuntimeError("Could not find a valid codesigning ID")
+
+    return codeSignID or "-"
+
+def GetCodeSignIDHash():
+    codeSignIDs = _GetCodeSignStringFromTerminal()
+    try:
+        return re.findall(r'\(.*?\)', codeSignIDs)[0][1:-1]
+    except:
+        raise Exception("Unable to parse codesign ID hash")
+
+def GetDevelopmentTeamID():
+    if os.environ.get("DEVELOPMENT_TEAM"):
+        return os.environ.get("DEVELOPMENT_TEAM")
+    codesignID = GetCodeSignIDHash()
+
+    certs = subprocess.check_output(["security", "find-certificate", "-c", codesignID, "-p"])
+    subject = GetCommandOutput(["openssl", "x509", "-subject"], input=certs)
+    subject = subject.splitlines()[0]
+
+    # Extract the Organizational Unit (OU field) from the cert
+    try:
+        team = [elm for elm in subject.split(
+            '/') if elm.startswith('OU')][0].split('=')[1]
+        if team is not None and team != "":
+            return team
+    except Exception as ex:
+        raise Exception("No development team found with exception " + ex)
+
+def CodesignFiles(files):
+    codeSignID = GetCodeSignID()
 
     for f in files:
         subprocess.call(['codesign', '-f', '-s', '{codesignid}'
-                              .format(codesignid=codeSignID), f],
+                        .format(codesignid=codeSignID), f],
                         stdout=devout, stderr=devout)
 
+
 def Codesign(install_path, verbose_output=False):
     if not MacOS():
         return False
@@ -217,3 +274,12 @@ def CreateUniversalBinaries(context, libNames, x86Dir, armDir):
                                 instDir=context.instDir, libName=targetName),
                        outputName)
     return lipoCommands
+
+def ConfigureCMakeExtraArgs(context, args:List[str]) -> List[str]:
+    system_name = None
+    if context.buildTarget == TARGET_IOS:
+        system_name = "iOS"
+
+    if system_name:
+        args.append(f"-DCMAKE_SYSTEM_NAME={system_name}")
+    return args

build_scripts/build_usd.py

@@ -252,7 +252,7 @@ def GetCPUCount():
     except NotImplementedError:
         return 1
 
-def Run(cmd, logCommandOutput = True):
+def Run(cmd, logCommandOutput = True, env = None):
     """Run the specified command in a subprocess."""
     PrintInfo('Running "{cmd}"'.format(cmd=cmd))
 
@@ -266,7 +266,7 @@ def Run(cmd, logCommandOutput = True):
         # code will handle them.
         if logCommandOutput:
             p = subprocess.Popen(shlex.split(cmd), stdout=subprocess.PIPE, 
-                                 stderr=subprocess.STDOUT)
+                                 stderr=subprocess.STDOUT, env=env)
             while True:
                 l = p.stdout.readline().decode(GetLocale(), 'replace')
                 if l:
@@ -421,6 +421,7 @@ def RunCMake(context, force, extraArgs = None):
             extraArgs.append('-DCMAKE_XCODE_ATTRIBUTE_ONLY_ACTIVE_ARCH=NO')
 
         extraArgs.append('-DCMAKE_OSX_ARCHITECTURES={0}'.format(targetArch))
+        extraArgs = apple_utils.ConfigureCMakeExtraArgs(context, extraArgs)
 
     if context.ignorePaths:
         ignoredPaths = ";".join(context.ignorePaths)
@@ -690,6 +691,19 @@ def AnyPythonDependencies(deps):
 
 def InstallZlib(context, force, buildArgs):
     with CurrentWorkingDirectory(DownloadURL(ZLIB_URL, context, force)):
+        # The following test files aren't portable to embedded platforms.
+        # They're not required for use on any platforms, so we elide them for efficiency
+        PatchFile("CMakeLists.txt",
+                  [("add_executable(example test/example.c)",
+                    ""),
+                   ("add_executable(minigzip test/minigzip.c)",
+                    ""),
+                   ("target_link_libraries(example zlib)",
+                    ""),
+                   ("target_link_libraries(minigzip zlib)",
+                    ""),
+                   ("add_test(example example)",
+                    "")])
         RunCMake(context, force, buildArgs)
 
 ZLIB = Dependency("zlib", InstallZlib, "include/zlib.h")
@@ -724,8 +738,8 @@ def InstallBoost_Helper(context, force, buildArgs):
     # However, there are some cases where a newer version is required.
     # - Building with Python 3.11 requires boost 1.82.0 or newer
     #   (https://github.com/boostorg/python/commit/a218ba)
-    # - Building on MacOS requires v1.82.0 or later for C++17 support starting 
-    #   with Xcode 15. We choose to use this version for all MacOS builds for 
+    # - Building on MacOS requires v1.82.0 or later for C++17 support starting
+    #   with Xcode 15. We choose to use this version for all MacOS builds for
     #   simplicity."
     # - Building with Python 3.10 requires boost 1.76.0 or newer
     #   (https://github.com/boostorg/python/commit/cbd2d9)
@@ -822,6 +836,10 @@ def InstallBoost_Helper(context, force, buildArgs):
             '--with-regex'
         ]
 
+        if MacOS() and context.buildTarget in apple_utils.EMBEDDED_PLATFORMS:
+            # Treat all embedded platforms as iphone derivatives since we're not actually building anything of note
+            b2_settings.append("target-os=iphone")
+
         if context.buildPython:
             b2_settings.append("--with-python")
             pythonInfo = GetPythonInfo(context)
@@ -1004,10 +1022,16 @@ def InstallTBB_MacOS(context, force, buildArgs):
         def _RunBuild(arch):
             if not arch:
                 return
-            makeTBBCmd = 'make -j{procs} arch={arch} {buildArgs}'.format(
+            platformArg = ""
+            env = os.environ.copy()
+            env["SDKROOT"] = apple_utils.GetSDKRoot(context)
+            if context.build_target in apple_utils.EMBEDDED_PLATFORMS:
+                platformArg = f"target={context.build_target}"
+            makeTBBCmd = 'make -j{procs} arch={arch} {platformArg} {buildArgs}'.format(
                 arch=arch, procs=context.numJobs,
+                platformArg=platformArg,
                 buildArgs=" ".join(buildArgs))
-            Run(makeTBBCmd)
+            Run(makeTBBCmd, env=env)
 
         _RunBuild(primaryArch)
         _RunBuild(secondaryArch)
@@ -2610,19 +2634,23 @@ def FormatBuildArguments(buildArgs):
     if context.macOSCodesign:
         apple_utils.Codesign(context.usdInstDir, verbosity > 1)
 
-Print("""
-Success! To use USD, please ensure that you have:""")
+printInstructions = any([context.buildPython, context.buildTools, context.buildPrman])
+if printInstructions:
+    Print("\nSuccess! To use USD, please ensure that you have:")
+else:
+    Print("\nSuccess! USD libraries were built.")
 
 if context.buildPython:
     Print("""
     The following in your PYTHONPATH environment variable:
     {requiredInPythonPath}""".format(
         requiredInPythonPath="\n    ".join(sorted(requiredInPythonPath))))
 
-Print("""
-    The following in your PATH environment variable:
-    {requiredInPath}
-""".format(requiredInPath="\n    ".join(sorted(requiredInPath))))
+if context.buildTools:
+    Print("""
+        The following in your PATH environment variable:
+        {requiredInPath}
+    """.format(requiredInPath="\n    ".join(sorted(requiredInPath))))
 
 if context.buildPrman:
     Print("See documentation at http://openusd.org/docs/RenderMan-USD-Imaging-Plugin.html "