build cross-compilers both for 64-bit host

build-mingw-w64.sh

@@ -2,11 +2,7 @@
 
 set -e
 
-# The Story So Far
+# We need two cross-compilers to build Proton:
-#
-# We need two cross-compilers to build Proton. These each have to run in the
-# Steam runtimes, each of which only supports 32- or 64-bit programs. Our build
-# VM is a 64-bit Linux machine. So our platform configurations are:
 #
 # 64-bit cross-compiler:
 #  Build (where the compiler is built): 64-bit linux (our VM)
@@ -15,109 +11,8 @@ set -e
 #
 # 32-bit cross-compiler:
 #  Build (where the compiler is built): 64-bit linux (our VM)
-#  Host (where the compiler is run):    32-bit linux (32-bit Steam runtime)
+#  Host (where the compiler is run):    64-bit linux (64-bit Steam runtime)
 #  Target (what the compiler outputs):  32-bit win32 (PE files to be run)
-#
-# The former is a pretty standard cross-compiler setup.
-#
-# gcc calls the latter, where all of the platforms are different, a "Canadian"
-# build. See "The GNU configure and build system" by Ian Lance Taylor, section
-# "Canadian Cross", available here:
-#     https://www.airs.com/ian/configure/configure_6.html
-#
-# This turned out to be quite difficult, possibly due to the added complexity of
-# mingw-w64. I'm documenting the problems I had and how I solved/worked around
-# them here, to hopefully save myself or someone else some heartburn in the
-# future. If you are a compiler expert and find yourself shaking your head at
-# this poor fool, I welcome your assistance improving this.
-#
-# Canadian builds require the build machine to already have a cross-compiler for
-# the Target platform available on the Build machine. Without this, the gcc build
-# will fail with:
-#
-#     i686-w64-mingw32-gcc -dumpspecs > tmp-specs
-#     /bin/bash: i686-w64-mingw32-gcc: command not found
-#
-# We are building both C and C++ lang support, so we need both gcc and g++
-# cross-compilers available. With the Build->Target cross-compilers installed,
-# we can now build gcc, and use that to build mingw-w64. After that, we need to
-# build gcc's libraries, like libgcc and libstdc++v3, against those mingw-w64
-# libraries.  However, the libatomic and/or libgomp builds will fail with:
-#
-#     checking for suffix of object files...
-#     configure: error: in `/home/vagrant/mingw/build-i686-w64-mingw32/gcc/i686-w64-mingw32/libatomic':
-#     configure: error: C compiler cannot create executables
-#     See `config.log' for more details
-#
-#     checking for suffix of object files...
-#     configure: error: in `/home/vagrant/mingw/build-i686-w64-mingw32/gcc/i686-w64-mingw32/libgomp':
-#     configure: error: C compiler cannot create executables
-#     See `config.log' for more details
-#
-# Digging into config.log shows it can't find libgcc:
-#
-#     configure:3722: checking whether the C compiler works
-#     configure:3744: i686-w64-mingw32-gcc -L/home/vagrant/mingw/output/i686-w64-mingw32/lib -L/home/vagrant/mingw/output/mingw/lib -isystem /home/vagrant/mingw/output/i686-w64-mingw32/include -isystem /home/vagrant/mingw/output/mingw/include    -g -O2   conftest.c  >&5
-#     /home/vagrant/mingw/output/lib/gcc/i686-w64-mingw32/9.2.0/../../../../i686-w64-mingw32/bin/ld: cannot find -lgcc
-#     /home/vagrant/mingw/output/lib/gcc/i686-w64-mingw32/9.2.0/../../../../i686-w64-mingw32/bin/ld: cannot find -lgcc_eh
-#     /home/vagrant/mingw/output/lib/gcc/i686-w64-mingw32/9.2.0/../../../../i686-w64-mingw32/bin/ld: cannot find -lgcc
-#     /home/vagrant/mingw/output/lib/gcc/i686-w64-mingw32/9.2.0/../../../../i686-w64-mingw32/bin/ld: cannot find -lgcc_eh
-#     collect2: error: ld returned 1 exit status
-#
-# I don't know what causes this (maybe Canadian builds don't like being split up
-# like this?). However, installing libgcc explicitly first will work around it.
-# After installing libgcc explicitly, we can then build the rest of gcc's
-# libraries. That was all the easy (ha!) stuff. At this point, you will have a
-# cross-compiler that will build Proton.
-#
-# However, there's a sneaky problem. For some reason the libstdc++v3 build system
-# requires libstdc++ to be available to detect C-lang functions(?!?). It will
-# still build without those C functions, but it may have far worse performance
-# (see Proton github issue #3198). You can detect this situation by examining the
-# config.log output for libstdc++v3 after your build completes:
-#
-#     configure:16811: checking for gettimeofday
-#     configure:16827: checking sys/time.h usability
-#     configure:16827:  i686-w64-mingw32-c++ -L/home/vagrant/mingw/output/i686-w64-mingw32/lib -L/home/vagrant/mingw/output/mingw/lib -isystem /home/vagrant/mingw/output/i686-w64-mingw32/include -isystem /home/vagrant/mingw/output/mingw/include    -c -g -O2 -fno-exceptions  conftest.cpp >&5
-#     configure:16827: $? = 0
-#     configure:16827: result: yes
-#     configure:16827: checking sys/time.h presence
-#     configure:16827:  i686-w64-mingw32-c++ -L/home/vagrant/mingw/output/i686-w64-mingw32/lib -L/home/vagrant/mingw/output/mingw/lib -isystem /home/vagrant/mingw/output/i686-w64-mingw32/include -isystem /home/vagrant/mingw/output/mingw/include    -E  conftest.cpp
-#     configure:16827: $? = 0
-#     configure:16827: result: yes
-#     configure:16827: checking for sys/time.h
-#     configure:16827: result: yes
-#     configure:16840: checking for gettimeofday
-#     configure:16875:  i686-w64-mingw32-c++ -L/home/vagrant/mingw/output/i686-w64-mingw32/lib -L/home/vagrant/mingw/output/mingw/lib -isystem /home/vagrant/mingw/output/i686-w64-mingw32/include -isystem /home/vagrant/mingw/output/mingw/include    -o conftest.exe -g -O2 -fno-exceptions   conftest.cpp  >&5
-#     /home/vagrant/mingw/output/lib/gcc/i686-w64-mingw32/9.2.0/../../../../i686-w64-mingw32/bin/ld: cannot find -lstdc++
-#     collect2: error: ld returned 1 exit status
-#
-# But that error doesn't kill configure, and it happily continues with this in
-# config.h:
-#
-#     /* #undef _GLIBCXX_USE_GETTIMEOFDAY */
-#
-# This triggers the bad codepath in libstdc++v3 that caused the performance
-# problem mentioned above, and is clearly wrong anyway, as gettimeofday is
-# definitely available. Yes, this was a huge pain to puzzle out. I "solved" this
-# by letting the libstdc++v3 build continue, then re-running the build after
-# installing it, so now it will find libstdc++ and so correctly detect the C-lang
-# function that has nothing at all to do with libstdc++. Argh.
-#
-# After all that, we finally have a functioning set of cross-compilers. Most of
-# the configuration parameters used here are taken from the Arch Linux mingw-w64
-# PKGBUILDs, as those were written by someone with more knowledge than me, and
-# have had a lot of testing. We make one tweak to the gcc configuration, which is
-# to disable SJLJ exceptions and enable DWARF2 debug symbols. The former
-# apparently helps with performance on 32-bit, and the latter puts debug symbols
-# in a format that more Linux tooling can read.
-#
-# Side note, the Arch Linux PKGBUILDs work very differently from how this script
-# works. While working on this, I tried to adapt the PKGBUILDs' process here
-# (e.g.  build a bootstrap C-lang compiler, use that to build mingw-w64, then
-# rebuild gcc against the mingw-w64 CRT with C++-lang support), but I ran into a
-# ton of problems, possibly caused by the Canadian-ness of the build, and
-# eventually ran out of ideas for working around them.
 
 if [ -z "$1" ]; then
     echo "Makes a local build of mingw-w64 in this directory and installs it to the given path."
@@ -315,7 +210,7 @@ setup_src
 
 mkdir -p $DST_DIR
 
-MINGW_W64_CRT_EXTRA_CONFIGURE="--disable-lib64 --enable-lib32" build_arch i686-linux-gnu i686-w64-mingw32
+MINGW_W64_CRT_EXTRA_CONFIGURE="--disable-lib64 --enable-lib32" build_arch x86_64-linux-gnu i686-w64-mingw32
 
 MINGW_W64_CRT_EXTRA_CONFIGURE="--disable-lib32 --enable-lib64" build_arch x86_64-linux-gnu x86_64-w64-mingw32