Merged PR 1111: Work around a break in incremental builds.

Incremental builds are broken in Mu release/201903 due to an improper use of unordered set() and dict() types.

By pinning the PYTHONHASHSEED prior to calling build.py, we ensure that the order is at least consistent from build to build.

MuEnvironment/UefiBuild.py

@@ -234,7 +234,17 @@ def Build(self):
         for key, value in buildvars.items():
             params += " -D " + key + "=" + value
         output_stream = MuLogging.create_output_stream()
+
+        env = ShellEnvironment.ShellEnvironment()
+        # WORKAROUND - Pin the PYTHONHASHSEED so that TianoCore build tools
+        #               have consistent ordering. Addresses incremental builds.
+        pre_build_env_chk = env.checkpoint()
+        env.set_shell_var('PYTHONHASHSEED', '0')
+        env.log_environment()
         ret = RunCmd("build", params)
+        # WORKAROUND - Undo the workaround.
+        env.restore_checkpoint(pre_build_env_chk)
+
         problems = MuLogging.scan_compiler_output(output_stream)
         MuLogging.remove_output_stream(output_stream)
         for level, problem in problems:

README.rst

@@ -25,6 +25,7 @@ Version History
 Main Changes:
 
 - Errors and warnings from the compiler are now intermingled and displayed in the order that they are emitted.
+- Add a workaround for incremental build break in Mu release/201903. Pinning PYTHONHASHSEED prevents unordered set() and dict() structures from changing build-to-build.
 
 
 0.3.8