Building on Windows in Release mode with official_build=false fails.

[mkarolin]

After merging C74 into master (#3502) building on Windows in Release mode with official_build=false produces the following link errors:

FAILED: nasm.exe nasm.exe.pdb
ninja -t msvc -e environment.x64 -- ../../third_party/llvm-build/Release+Asserts/bin/lld-link.exe /nologo /OUT:./nasm.exe /PDB:./nasm.exe.pdb @./nasm.exe.rsp
lld-link: error: duplicate symbol: ilog2_32 in obj/third_party/nasm/nasm/directiv.obj and in obj/third_party/nasm/nasm/ilog2.obj
lld-link: error: duplicate symbol: ilog2_64 in obj/third_party/nasm/nasm/directiv.obj and in obj/third_party/nasm/nasm/ilog2.obj
lld-link: error: duplicate symbol: alignlog2_32 in obj/third_party/nasm/nasm/ilog2.obj and in obj/third_party/nasm/nasm/outmacho.obj

cc: @emerick

[mkarolin]

• Both the latest C73 and C74 use the same nasm code (commit 4ee6a69c).
• The compilation flags for Release mode with official_build=false have not changed (/Od /Ob0 /GF).
• The Clang version has changed (from 351477 to 354873).

Rolling back to Clang 351477 eliminates the errors.

[mkarolin]

When linking with /VERBOSE there is a bit more info:
lld-link: conflicting comdat type for ilog2_32: 2 in obj/third_party/nasm/nasm/directiv.obj and 1 in obj/third_party/nasm/nasm/ilog2.obj lld-link: error: duplicate symbol: ilog2_32 in obj/third_party/nasm/nasm/directiv.obj and in obj/third_party/nasm/nasm/ilog2.obj

1 and 2 refer to

enum COMDATType {
    IMAGE_COMDAT_SELECT_NODUPLICATES = 1,
    IMAGE_COMDAT_SELECT_ANY,
    IMAGE_COMDAT_SELECT_SAME_SIZE,
    IMAGE_COMDAT_SELECT_EXACT_MATCH,
    IMAGE_COMDAT_SELECT_ASSOCIATIVE,
    IMAGE_COMDAT_SELECT_LARGEST,
    IMAGE_COMDAT_SELECT_NEWEST
  };

Recent llvm changes of note:

https://reviews.llvm.org/D58180
https://bugs.llvm.org/show_bug.cgi?id=40094 (see all changes at the bottom)

[mkarolin]

Also, notice this change in nasm from Nov 2018 where config for windows was switched from config/config-win.h to config/msvc.h (https://chromium.googlesource.com/chromium/deps/nasm.git/+/274b50137b6209b106f8989a24ab92f287654147). Of note in this case is that config-win.h had #define HAVE_STDC_INLINE 1 whereas msvc.h doesn't. This means that on windows none of the functions declared in ilog2.h are inline.

[rebron]

Closing. Reopen if this happens again.

[mkarolin]

This will be addressed by #3502 (re-landing of C74 with LLVM reverted to 351477).