Squashed 'boost/' content from commit b4feb19f2

git-subtree-dir: boost
git-subtree-split: b4feb19f287ee92d87a9624b5d36b7cf46aeadeb

tools/build/example/try_compile/Jamroot.jam

@@ -0,0 +1,29 @@
+
+# This example shows performing configure checks in Boost.Build,
+# e.g. to check for some system function or compiler quirk.
+
+# First, declare a metatarget that we'll try to build.
+obj foo : foo.cpp ;
+# Make it explicit so that it's only built if used by a configure check
+explicit foo ;
+
+# Declare a target that depends on configure check result.
+exe main 
+    : main.cpp 
+    # The check-target-builds invocation in requirements section will
+    # - build the specified metatarget
+    # - if it builds OK, add the properties in the second parameter
+    # - otherwise, add the properties in the third parameter
+    : [ check-target-builds foo : <define>FOO=1 : <define>FOO=0 ]
+    ;
+
+# To test this:
+#
+# 1. Build with "b2". You should see a "foo builds: yes" message, and running
+#    the produced executable will show that FOO is set to 1.
+# 2. Modify foo.cpp to contain a compile error, rebuild with
+#    "b2 -a --reconfigure". You should see a "foo builds: no" message, and running
+#    the produced executable should show that FOO is now set to 0.
+#
+# The output from the check is not shown on the console, instead it is
+# redirected to the bin/config.log file

tools/build/example/try_compile/foo.cpp

@@ -0,0 +1,6 @@
+
+
+int foo()
+{
+   return 0;
+}

tools/build/example/try_compile/main.cpp

@@ -0,0 +1,8 @@
+
+#include <iostream>
+using namespace std;
+
+int main()
+{
+    std::cout << "Foo: " << FOO << "\n";
+}