[gjs/master.msvc: 4/4] README.MSVC.md: Update build instructions

[Chun-wei Fan <fanchunwei src gnome org>]

commit bbacf965693559e97a268c36649a1105ef6b6370
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Wed Feb 5 16:48:15 2020 +0800

    README.MSVC.md: Update build instructions
    
    Let people know how SpiderMonkey 68 can be built, since it now requires CLang
    for compilation, and additional ways to obtain the SpiderMonkey sources.
    
    Unfortunately, some GCCisms and CLangisms creeped into the public headers
    of the SpiderMonkey 68 public headers, so they must be updated first before
    carrying out the build of GJS, which are being described here, and it is
    currently not possible to build GJS with CLang on Windows.
    
    Note that since CLang link to the same CRT DLLs as Visual Studio 2017 and 2019,
    it is perfectly fine to build and link GJS against SpiderMonkey 68 with
    the Visual Studio 2017/2019 builds of GJS, when the needed updates to the
    SpiderMonkey headers are applied, as described above.

 README.MSVC.md | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 56 insertions(+), 3 deletions(-)
---
diff --git a/README.MSVC.md b/README.MSVC.md
index 7ee37cab..c513c4d8 100644
--- a/README.MSVC.md
+++ b/README.MSVC.md
@@ -6,7 +6,7 @@ via Meson.  Due to C++-14 usage, Visual Studio 2017 15.6.x or later is
 required, as the compiler flag /Zc:externConstexpr is needed.
 
 You will need the following items to build GJS using Visual Studio:
--SpiderMonkey 68 (mozjs-68).  Please see the below section carefully 
+-SpiderMonkey 68.4.x (mozjs-68).  Please see the below section carefully 
  on this...
 -GObject-Introspection (G-I) 1.61.2 or later
 -GLib 2.58.x or later, (which includes GIO, GObject, and the associated tools)
@@ -28,6 +28,13 @@ for the suitable release series of SpiderMonkey that corresponds to
 the GJS version that is being built, as GJS depends on ESR (Extended 
 Service Release, a.k.a Long-term support) releases of SpiderMonkey.
 
+You may also be able to obtain the SpiderMonkey 68.4.x sources via the
+FireFox (ESR) or Thunderbird 68.4.x sources, in $(srcroot)/js.  Since
+this release of Firefox/Thunderbird/SpiderMonkey requires clang-cl
+from the LLVM project, you will need to install LLVM/CLang from the
+LLVM website and ensure that clang.exe can be found in your PATH in
+order to build SpiderMonkey 68.4.x.
+
 Please do note that the build must be done carefully, in addition to the
 official instructions that are posted on the Mozilla website:
 
@@ -36,10 +43,10 @@ https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Build_Doc
 For the configuration step, you will need to run the following:
 
 (64-bit/x64 builds)
-JS_STANDALONE=1 $(mozjs_srcroot)/js/src/configure --enable-nspr-build --host=x86_64-pc-mingw32 
--target=x86_64-pc-mingw32 --prefix=--prefix=<some_prefix> --disable-jemalloc
+JS_STANDALONE=1 $(mozjs_srcroot)/js/src/configure --enable-nspr-build --host=x86_64-pc-mingw32 
--target=x86_64-pc-mingw32 --prefix=--prefix=<some_prefix> --disable-jemalloc 
--with-libclang-path=<full_path_to_directory_containing_x64_libclang_dll> 
--with-clang-path=<full_path_to_directory_containing_x64_clang_exe>
 
 (32-bit builds)
-JS_STANDALONE=1 $(mozjs_srcroot)/js/src/configure --enable-nspr-build --prefix=<some_prefix> 
--disable-jemalloc
+JS_STANDALONE=1 $(mozjs_srcroot)/js/src/configure --enable-nspr-build --host=i686-pc-mingw32 
--target=i686-pc-mingw32 --prefix=<some_prefix> --disable-jemalloc 
--with-libclang-path=<full_path_to_directory_containing_x86_libclang_dll> 
--with-clang-path=<full_path_to_directory_containing_x86_clang_exe>
 
 Notice that "JS_STANDALONE=1" and "--disable-jemalloc" are absolutely required,
 otherwise GJS will not build/run correctly.  If your GJS build crashes upon
@@ -94,6 +101,52 @@ will also need to ensure that the existing GObject-Introspection
 installation (if used) is on the same drive where the GJS sources
 are (and therefore where the GJS build is being carried out).
 
+Since Mozilla insisted that clang-cl is to be used to build SpiderMonkey,
+note that some SpideMonkey headers might need be updated as follows, before
+or after building SpiderMonkey, since there are some GCC-ish assumptions
+here:
+
+-Update $(includedir)/mozjs-68/mozilla/DbgMacro.h:
+
+// Change this... (ca. line 174)
+#ifndef MOZILLA_OFFICIAL
+#  define MOZ_DBG(expression_...) \
+    mozilla::detail::MozDbg(__FILE__, __LINE__, #expression_, expression_)
+#endif
+
+//To this...
+#ifndef MOZILLA_OFFICIAL
+#  define MOZ_DBG(...) \
+    mozilla::detail::MozDbg(__FILE__, __LINE__, #__VA_ARGS__, __VA_ARGS__)
+#endif
+
+// And change this... (ca. line 197)
+#define MOZ_DEFINE_DBG(type_, members_...)                                   \
+  friend std::ostream& operator<<(std::ostream& aOut, const type_& aValue) { \
+    return aOut << #type_                                                    \
+                << (MOZ_ARG_COUNT(members_) == 0 ? "" : " { ")               \
+                       MOZ_FOR_EACH_SEPARATED(MOZ_DBG_FIELD, (<< ", "), (),  \
+                                              (members_))                    \
+                << (MOZ_ARG_COUNT(members_) == 0 ? "" : " }");               \
+  }
+
+// To this...
+#define MOZ_DEFINE_DBG(type_, ...)                                   \
+  friend std::ostream& operator<<(std::ostream& aOut, const type_& aValue) { \
+    return aOut << #type_                                                    \
+                << (MOZ_ARG_COUNT(__VA_ARGS__) == 0 ? "" : " { ")               \
+                       MOZ_FOR_EACH_SEPARATED(MOZ_DBG_FIELD, (<< ", "), (),  \
+                                              (__VA_ARGS__))                    \
+                << (MOZ_ARG_COUNT(__VA_ARGS__) == 0 ? "" : " }");               \
+  }
+
+
+-Update $(includedir)/mozjs-68/js/AllocPolicy.h (after the build):
+
+Get rid of the 'JS_FRIEND_API' macro from the class
+'TempAllocPolicy : public AllocPolicyBase' (ca. line 110 and 175),
+for the member method definitions of onOutOfMemory() and reportAllocOverflow()
+
 ======================
 To carry out the build
 ======================