[build] Don't use ls(1) to find JDK paths (#314)

Fixes: dotnet/android#1493

On some machines, `make prepare` fails:

	build-tools/scripts/jdk.mk:130: *** missing separator.  Stop.
	make: *** [prepare-external] Error 2

Eventually, we "found" the "cause": This make fragment:

	$(shell ls -dtr $(_DARWIN_JDK_FALLBACK_DIRS) | sort | tail -1)

was dying a terrible horrible no good death:

	_DARWIN_JDK_ROOT=/Library/Java/JavaVirtualMachines/jdk1.8.0_161.jdk
	kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkin/sh: 49m: command not found

[Turns Out™][0], **ls**(1) should be *avoided*, as its output is
*unsafe* (I'm not sure *why*, and I'm not able to repro the above
failure on my machine, but it's *clearly* bad).

[0]: http://mywiki.wooledge.org/ParsingLs

Why are we using **ls**(1)?  To sort by timestamp, via `ls -dtr`.
What's the recommended replacement?

> If you truly need a list of all the files in a directory in order
> by mtime so that you can process them in sequence, switch to perl,
> and have your perl program do its own directory opening and sorting

LOL?

Which brings us to the solution: we don't want to use Perl -- we
*want* something plausibly cross-platform -- so let's use our existing
cross-platform dependency: MSBuild!

Update the `<JdkInfo/>` task so that in addition to probing a variety
of Windows-specific registry locations, it can now do `jdk.mk`-style
directory probing, allowing us to find the maximum installed JDK
version which is (optionally) less than `$(JI_MAX_JDK)`.

Additionally, further enhance `<JdkInfo/>` so that it will *also*
check `$JAVA_HOME` and execute the following command:

	java -XshowSettings:properties -version 2>&1 | grep java.home

`$JAVA_HOME` is preferred, if specified and it fulfills the
requirements of `$(JI_MAX_JDK)`.

Additionally, drastically simplify `jdk.mk`.  Instead of computing the
desired JDK directory *on every build*, instead generate a new
`bin/Build$(CONFIGURATION)/JdkInfo.mk` file which contains the JDK
informatino.  The `make prepare` target will generate this file.

This approach simplifes `jdk.mk` -- trying to maintain it was
beginning to give me a headache, so as part of this we're dropping
support for 32-bit JVMs on macOS, as if anyone uses those -- and also
brings the macOS/Linux build closer-in-spirit to Windows, which was
already using the `<JdkInfo/>` task.

Author: jonpryor

Makefile

@@ -53,7 +53,15 @@ xa-all: $(PACKAGES) $(XA_INTEGRATION_OUTPUTS)
 
 run-all-tests: run-tests run-test-jnimarshal run-test-generator-core run-ptests
 
-prepare:: prepare-external
+include build-tools/scripts/msbuild.mk
+
+prepare:: prepare-bootstrap prepare-external
+
+prepare-bootstrap: bin/Build$(CONFIGURATION)/Java.Interop.BootstrapTasks.dll
+
+bin/Build$(CONFIGURATION)/Java.Interop.BootstrapTasks.dll: src/Java.Interop.BootstrapTasks/Java.Interop.BootstrapTasks.csproj \
+		$(wildcard src/Java.Interop.BootstrapTasks/Java.Interop.BootstrapTasks/*.cs)
+	$(MSBUILD) $(MSBUILD_FLAGS) src/Java.Interop.BootstrapTasks/Java.Interop.BootstrapTasks.csproj
 
 prepare-external: $(PACKAGES) $(NUNIT_CONSOLE)
 	git submodule update --init --recursive
@@ -65,7 +73,6 @@ clean:
 
 include build-tools/scripts/mono.mk
 include build-tools/scripts/jdk.mk
-include build-tools/scripts/msbuild.mk
 
 $(PACKAGES) $(NUNIT_CONSOLE):
 	nuget restore

build-tools/scripts/PrepareWindows.targets

@@ -19,8 +19,12 @@
         DestinationFiles="$(_NuGet)"
     />
     <Exec Command="$(_NuGet) restore Java.Interop.sln" WorkingDirectory="$(_TopDir)" />
-    <JdkInfo Output="$(_TopDir)\bin\Build$(Configuration)\JdkInfo.props">
-      <Output TaskParameter="JavaSdkDirectory" PropertyName="_JavaSdkDirectory" />
+    <JdkInfo
+        JdksRoot="$(ProgramFiles)\Java"
+        MakeFragmentFile="$(MSBuildThisFileDirectory)..\..\bin\Build$(Configuration)\JdkInfo.mk"
+        MaximumJdkVersion="$(JI_MAX_MDK)"
+        PropertyFile="$(_TopDir)\bin\Build$(Configuration)\JdkInfo.props">
+      <Output TaskParameter="JavaHomePath" PropertyName="_JavaSdkDirectory" />
     </JdkInfo>
   </Target>
 </Project>

build-tools/scripts/jdk.mk

@@ -26,157 +26,22 @@
 #       Location of the JDK `/bin` directory, which contains `java/`javac`/etc.
 
 OS           ?= $(shell uname)
-JI_JAVAC_PATH = javac
-JI_JAR_PATH   = jar
 
-JI_JDK_BIN_PATH = $(dir $(shell which java))
+_INCLUDE_MK = bin/Build$(CONFIGURATION)/JdkInfo.mk
 
+prepare:: $(_INCLUDE_MK)
 
-# Filter on <= JI_MAX_JDK
-ifneq ($(JI_MAX_JDK),)
-_VERSION_MAX  := | awk '$$1 <= $(JI_MAX_JDK)'
-endif #JI_MAX_JDK
-
-# Sort numerically on version numbers with `sort -n`, filtering on $(JI_MAX_JDK) if needed
-# Replace each line so it starts with a number (sed 's/...'\1 &/), sort on the leading number, then remove the leading number.
-# Grab the last path name printed.
-_VERSION_SORT := sed 's/[^0-9]*\([0-9.]*\)/\1 &/' $(_VERSION_MAX) | sort -n | sed 's/^[0-9.]* //g' | tail -1
+-include $(_INCLUDE_MK)
 
 ifeq ($(OS),Darwin)
-
-_MONO_BITNESS = $(shell file `which $(word 1, $(RUNTIME))` | awk 'BEGIN { val = "32-bit" } /64-bit/ { val = "64-bit" } END { print val; }')
-
-ifeq ($(_MONO_BITNESS),32-bit)
-# The only 32-bit JVM I know of is the Apple-provided one.
-JI_JVM_PATH	= /System/Library/Frameworks/JavaVM.framework/JavaVM
-endif # 32-bit
-
-# Darwin supports three possible search locations:
-#
-# 1. `/Library/Java/JavaVirtualMachines/jdk*`
-#     These are where 3rd party JDKs are installed, such as the Oracle JDK.
-#     This is the preferred search directory.
-#
-# 2. The Xcode.app MacOSX.platform SDK, which is for the ancient JDK6 that
-#     continues to be available
-#
-# 3. A "locally" hosted .pkg, in case Xcode.app isn't installed.
-
-_DARWIN_JDK_FALLBACK_DIRS         = $(wildcard /Library/Java/JavaVirtualMachines/jdk*)
-_DARWIN_JDK_JNI_INCLUDE_DIR       = Contents/Home/include
-_DARWIN_JDK_JNI_OS_INCLUDE_DIR    = $(_DARWIN_JDK_JNI_INCLUDE_DIR)/darwin
-
-_XCODE_APP_JAVAVM_FRAMEWORK_PATH  = \
-	$(word 1, $(wildcard /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX*.sdk/System/Library/Frameworks/JavaVM.framework/Headers))
-
-
-_LOCAL_JDK_PKG                    = JavaDeveloper-2013005_dp__11m4609.pkg
-_LOCAL_JDK_URL                    = http://storage.bos.xamarin.com/android-sdk-tool/archives/$(FALLBACK_JDK_PKG)
-_LOCAL_JDK_HEADERS                = LocalJDK/System/Library/Frameworks/JavaVM.framework/Versions/A/Headers
-
-# Ancient source for (3)
-_APPLE_JDK6_URL                   = http://adcdownload.apple.com/Developer_Tools/java_for_os_x_2013005_developer_package/java_for_os_x_2013005_dp__11m4609.dmg
-
-ifneq ($(_DARWIN_JDK_FALLBACK_DIRS),)
-_DARWIN_JDK_ROOT      := $(shell ls -dtr $(_DARWIN_JDK_FALLBACK_DIRS) | $(_VERSION_SORT))
-JI_JDK_BIN_PATH       = $(_DARWIN_JDK_ROOT)/Contents/Home/bin
-JI_JAVAC_PATH         = $(_DARWIN_JDK_ROOT)/Contents/Home/bin/javac
-JI_JAR_PATH           = $(_DARWIN_JDK_ROOT)/Contents/Home/bin/jar
-JI_JDK_INCLUDE_PATHS  = \
-	$(_DARWIN_JDK_ROOT)/$(_DARWIN_JDK_JNI_INCLUDE_DIR) \
-	$(_DARWIN_JDK_ROOT)/$(_DARWIN_JDK_JNI_OS_INCLUDE_DIR)
-
-ifeq ($(_MONO_BITNESS),64-bit)
-JI_JVM_PATH	= $(shell find $(_DARWIN_JDK_ROOT)/Contents/Home -name libjli.dylib)
-endif # 64-bit
-
-else    # (1) failed; try Xcode.app's copy?
-ifneq ($(_XCODE_APP_JAVAVM_FRAMEWORK_PATH),)
-JI_JDK_INCLUDE_PATHS  = $(_XCODE_APP_JAVAVM_FRAMEWORK_PATH)
-else    # (2) failed; hail mary pass!
-JI_JDK_INCLUDE_PATHS  = LocalJDK/System/Library/Frameworks/JavaVM.framework/Versions/A/Headers
-
-bin/Build$(CONFIGURATION)/JdkHeaders.props: $(JI_JDK_INCLUDE_PATHS)/jni.h
-
-$(JI_JDK_INCLUDE_PATHS)/jni.h:
-	@if [ ! -f $(_LOCAL_JDK_PKG) ]; then \
-		curl -o $(_LOCAL_JDK_PKG) $(_LOCAL_JDK_URL) ; \
-	fi
-	-mkdir LocalJDK
-	_jdk="$$(cd `dirname "$(_LOCAL_JDK_PKG)"`; pwd)/`basename "$(_LOCAL_JDK_PKG)"`" ; \
-	(cd LocalJDK; xar -xf $$_jdk)
-	(cd LocalJDK; gunzip -c JavaEssentialsDev.pkg/Payload | cpio -i)
-endif   # (3)
-endif   # (1)
-
-endif   # Darwin
-
+_JDKS_ROOT  := /Library/Java/JavaVirtualMachines
+endif # $(OS)=Darwin
 
 ifeq ($(OS),Linux)
+_JDKS_ROOT  := /usr/lib/jvm
+endif # $(OS)=Linux
 
-# This is for all linux distributions with which and java installed
-_DEFAULT_LINUX_JAVA_ROOT          = $(shell java -XshowSettings:properties -help 2>&1 | grep java.home | sed 's/^.*java.home = //g')/../
-_DEFAULT_LINUX_JAVA_INCLUDE_DIRS  = $(_DEFAULT_LINUX_JAVA_ROOT)/include/
-_LINUX_JAVA_FALLBACK_DIRS         = /usr/lib/jvm/java*
-_LINUX_JAVA_JNI_INCLUDE_DIR       = include
-_LINUX_JAVA_ROOT                  = $(_DEFAULT_LINUX_JAVA_ROOT)
-_LINUX_JAVA_ARCH_64               = amd64
-_LINUX_JAVA_ARCH_32               = i386
-
-_DESKTOP_JAVA_INCLUDE_DIRS = $(_DEFAULT_LINUX_JAVA_INCLUDE_DIRS)
-
-ifeq ($(wildcard $(_DESKTOP_JAVA_INCLUDE_DIRS)),)
-_DESKTOP_JAVA_INCLUDE_DIRS  = $(wildcard $(JAVA_HOME)/include)
-_LINUX_JAVA_ROOT            = $(JAVA_HOME)
-endif # No default Java location, $JAVA_HOME check
-
-ifeq ($(wildcard $(_DESKTOP_JAVA_INCLUDE_DIRS)),)
-LATEST_JDK                  := $(shell ls -dtr $(_LINUX_JAVA_FALLBACK_DIRS) | $(_VERSION_SORT))
-_DESKTOP_JAVA_INCLUDE_DIRS  = $(LATEST_JDK)/$(_LINUX_JAVA_JNI_INCLUDE_DIR)
-_LINUX_JAVA_ROOT            = $(LATEST_JDK)
-endif # No $JAVA_HOME, find the latest version
-
-JI_JDK_INCLUDE_PATHS = $(_DESKTOP_JAVA_INCLUDE_DIRS) $(_DESKTOP_JAVA_INCLUDE_DIRS)/linux
-
-ifneq ($(wildcard $(_LINUX_JAVA_ROOT)/jre/lib/$(_LINUX_JAVA_ARCH_64)/server/libjvm.so),)
-JI_JVM_PATH                 = $(_LINUX_JAVA_ROOT)/jre/lib/$(_LINUX_JAVA_ARCH_64)/server/libjvm.so
-endif # Find 64-bit libjvm
-
-ifeq ($(JI_JVM_PATH),) # (1) No 64-bit java arch
-ifneq ($(wildcard $(_LINUX_JAVA_ROOT)/jre/lib/$(_LINUX_JAVA_ARCH_32)/server/libjvm.so),) # (2) check 32-bit instead, even on a 64-bit system
-JI_JVM_PATH                 = $(_LINUX_JAVA_ROOT)/jre/lib/$(_LINUX_JAVA_ARCH_32)/server/libjvm.so
-endif # (2)
-endif # (1)
-
-JI_JDK_BIN_PATH             = $(_LINUX_JAVA_ROOT)/bin
-JI_JAVAC_PATH               = $(_LINUX_JAVA_ROOT)/bin/javac
-JI_JAR_PATH                 = $(_LINUX_JAVA_ROOT)/bin/jar
-
-endif   # Linux
-
-$(JI_JVM_PATH):
-	@echo "error: No JVM found\!";
-	@exit 1
-
-bin/Build$(CONFIGURATION)/JdkInfo.props: $(JI_JDK_INCLUDE_PATHS) $(JI_JVM_PATH)
-	-mkdir -p `dirname "$@"`
-	-rm "$@"
-	echo '<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">' > "$@"
-	echo '  <Choose>' >> "$@"
-	echo "    <When Condition=\" '\$$(JdkJvmPath)' == '' \">" >> "$@"
-	echo '      <PropertyGroup>' >> "$@"
-	echo "        <JdkJvmPath>$(JI_JVM_PATH)</JdkJvmPath>" >> "$@"
-	echo '      </PropertyGroup>' >> "$@"
-	echo '      <ItemGroup>' >> "$@"
-	for p in $(JI_JDK_INCLUDE_PATHS); do \
-		echo "        <JdkIncludePath Include=\"$$p\" />" >> "$@"; \
-	done
-	echo '      </ItemGroup>' >> "$@"
-	echo '    </When>' >> "$@"
-	echo '  </Choose>' >> "$@"
-	echo '  <PropertyGroup>' >> "$@"
-	echo "    <JdkBinPath Condition=\" '\$$(JdkBinPath)' == '' \">$(JI_JDK_BIN_PATH)</JdkBinPath>" >> "$@"
-	echo "    <JavaCPath Condition=\" '\$$(JavaCPath)' == '' \">$(JI_JAVAC_PATH)</JavaCPath>" >> "$@"
-	echo "    <JarPath Condition=\" '\$$(JarPath)' == '' \">$(JI_JAR_PATH)</JarPath>" >> "$@"
-	echo '  </PropertyGroup>' >> "$@"
-	echo '</Project>' >> "$@"
+$(_INCLUDE_MK): bin/Build$(CONFIGURATION)/Java.Interop.BootstrapTasks.dll
+	$(MSBUILD) $(MSBUILD_FLAGS) build-tools/scripts/jdk.targets /t:GetPreferredJdkRoot \
+		/p:JdksRoot="$(_JDKS_ROOT)" \
+		$(if $(JI_MAX_JDK),"/p:MaximumJdkVersion=$(JI_MAX_JDK)")

build-tools/scripts/jdk.targets

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <UsingTask  TaskName="Java.Interop.BootstrapTasks.JdkInfo"  AssemblyFile="$(MSBuildThisFileDirectory)..\..\bin\Build$(Configuration)\Java.Interop.BootstrapTasks.dll" />
+  <Target Name="GetPreferredJdkRoot">
+    <JdkInfo
+        JdksRoot="$(JdksRoot)"
+        MakeFragmentFile="$(MSBuildThisFileDirectory)..\..\bin\Build$(Configuration)\JdkInfo.mk"
+        MaximumJdkVersion="$(MaximumJdkVersion)"
+        PropertyFile="$(MSBuildThisFileDirectory)..\..\bin\Build$(Configuration)\JdkInfo.props">
+      <Output TaskParameter="JavaHomePath" PropertyName="_JavaHome"/>
+    </JdkInfo>
+  </Target>
+</Project>

src/Java.Interop.BootstrapTasks/Java.Interop.BootstrapTasks.csproj

@@ -33,15 +33,17 @@
     <Reference Include="System" />
     <Reference Include="System.Net.Http" />
     <Reference Include="System.Xml" />
+    <Reference Include="System.Xml.Linq" />
     <Reference Include="Microsoft.Build.Framework" />
     <Reference Include="Microsoft.Build.Utilities.v4.0" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="Java.Interop.BootstrapTasks\DownloadUri.cs" />
     <Compile Include="Java.Interop.BootstrapTasks\JdkInfo.cs" />
+    <Compile Include="Java.Interop.BootstrapTasks\OS.cs" />
     <Compile Include="Java.Interop.BootstrapTasks\RegistryEx.cs" />
-    <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Java.Interop.BootstrapTasks\SetEnvironmentVariable.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
 </Project>