Merge pull request #5028 from RoryO/msvc-optimize-shuffle-bug

Work around MSC optimization generating non functional code with Array#shuffle

.github/workflows/build.yml

@@ -101,6 +101,3 @@ jobs:
         rake -E "STDOUT.sync=true" -m -j4 test
       env:
         MRUBY_CONFIG: appveyor_config.rb
-        # TODO(take-cheeze): Re-enable /O2
-        CFLAGS: "/c /nologo /W3 /we4013 /Zi /MD /D_CRT_SECURE_NO_WARNINGS"
-        CXXFLAGS: "/c /nologo /W3 /Zi /MD /EHs /D_CRT_SECURE_NO_WARNINGS"

appveyor.yml

 version: "{build}"
 
-os: Visual Studio 2017
-
 shallow_clone: true
 
 environment:
   matrix:
-    # Visual Studio 2017 64bit
-    - visualcpp: C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars64.bat
-
-    # Visual Studio 2017 32bit
-    - visualcpp: C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvarsall.bat
+    - job_name: Visual Studio 2019 64bit
+      visualcpp: C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat
+      appveyor_build_worker_image: Visual Studio 2019
+
+    - job_name: Visual Studio 2019 32bit
+      visualcpp: C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars32.bat
+      appveyor_build_worker_image: Visual Studio 2019
+
+    - job_name: Visual Studio 2017 64bit
+      visualcpp: C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars64.bat
+      appveyor_build_worker_image: Visual Studio 2017
+
+    - job_name: Visual Studio 2017 32bit
+      visualcpp: C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars32.bat
+      appveyor_build_worker_image: Visual Studio 2017
+
+    - job_name: Visual Studio 2015 64bit
+      visualcpp: C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat
+      appveyor_build_worker_image: Visual Studio 2015
+      machine: x86_amd64
+
+    - job_name: Visual Studio 2015 32bit
+      visualcpp: C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat
+      appveyor_build_worker_image: Visual Studio 2015
       machine: x86
 
-    # Visual Studio 2015 64bit
-    - visualcpp: C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat
-      machine: amd64
-
-    # Visual Studio 2015 32bit
-    - visualcpp: C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat
-      machine: x86
-
-    # Visual Studio 2013 64bit
-    - visualcpp: C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat
-      machine: amd64
-
+    - job_name: Visual Studio 2013 64bit
+      visualcpp: C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat
+      appveyor_build_worker_image: Visual Studio 2015
+      machine: x86_amd64
 
 init:
   - call "%visualcpp%" %machine%
-  # For using Rubyinstaller's Ruby 2.4 64bit
-  - set PATH=C:\Ruby24-x64\bin;%PATH%
+  # For using Rubyins4aller's Ruby 2.6 64bit
+  # 2.6 is the highest supported Ruby version across all historical
+  # Visual Studio AppVeyor images. Ruby 2.7 is only on the 2019 image.
+  - set PATH=C:\Ruby26-x64\bin;%PATH%
   - ruby --version
 
-
 build_script:
   - set MRUBY_CONFIG=appveyor_config.rb
-  - rake -m
-  - rake -E $stdout.sync=true test
+  - rake -E "$stdout.sync=true" -m -j4 test

mrbgems/mruby-random/src/random.c

@@ -218,6 +218,34 @@ mrb_ary_shuffle_bang(mrb_state *mrb, mrb_value ary)
   mrb_value r = mrb_nil_value();
   rand_state *random;
 
+ /*
+ * MSC compiler bug generating invalid instructions with optimization
+ * enabled. MSC errantly uses a hardcoded value with optimizations on
+ * when using a fixed value from a union.
+ * Creating a temp volatile variable and reassigning back to the original
+ * value tricks the compiler to not perform this optimization;
+ */
+#if defined _MSC_VER && _MSC_VER >= 1923
+  /* C++ will not cast away volatile easily, so we cannot do something like
+   * volatile mrb_value rr = r; r = (mrb_value)rr; with C++.
+   * That cast does work with C.
+   * We also have to trick the compiler to not optimize away the const_cast entirely
+   * by creating and manipulating an intermediate volatile pointer.
+   */
+  volatile mrb_value *v_r;
+  volatile mrb_int ii;
+  mrb_value *p_r;
+  v_r = &r;
+  ii = 2;
+  v_r = v_r + 2;
+#if defined __cplusplus
+  p_r = const_cast<mrb_value*>(v_r - ii);
+#else
+  p_r = (mrb_value*)v_r - ii;
+#endif
+  r = *p_r;
+#endif
+
   if (RARRAY_LEN(ary) > 1) {
     mrb_get_args(mrb, "|o", &r);