SCons: Disable misbehaving MSVC incremental linking

[akien-mga]

Fixes #77968.

Testing welcome from MSVC users, to see both whether you could reproduce #77968 and confirm this fixes it, or if you couldn't reproduce it, confirm that it speeds up or doesn't slow down your linking time.

[YuriSizov]

I've repeated my experiment from here. I used the same commit and applied this change directly. It resulted in subsequent builds being twice as fast as before (45-50 seconds faster).

Fresh build (reset using git clean -dfxi)
[Time elapsed: 00:02:30.193]

1 new line 🧛
[Time elapsed: 00:00:45.407]

2 new lines 🧛🧛
[Time elapsed: 00:00:44.263]

3 new lines 🧛🧛🧛
[Time elapsed: 00:00:44.248]

4 new lines 🧛🧛🧛🧛
[Time elapsed: 00:00:44.745]

Empty build (no changes compared to above)
[Time elapsed: 00:00:06.146]

Out of curiosity I've removed the patch, and it's the same as before with noticeably longer linking times:

Fresh build (reset using git clean -dfxi)
[Time elapsed: 00:02:01.338]

1 new line 🧛
[Time elapsed: 00:01:33.458]

2 new lines 🧛🧛
[Time elapsed: 00:01:35.264]

3 new lines 🧛🧛🧛
[Time elapsed: 00:01:38.123]

4 new lines 🧛🧛🧛🧛
[Time elapsed: 00:01:34.067]

Empty build (no changes compared to above)
[Time elapsed: 00:00:06.188]

I'm not sure why the initial build is slightly slower now, but that's a fair trade-off if that's what we have for subsequent builds. (Note that in the linked issue my initial time is way too slow because I wasn't plugged in until mid-through the build.)

[darksylinc]

This PR may have caused issues when compiling with:

scons p=windows vsproj=yes optimize=none debug_symbols=True tests=False dev_mode=True dev_build=True

I keep getting silly errors like this one:

console_wrapper_windows.windows.editor.dev.x86_64.obj : warning LNK4099: PDB 'vc140.pdb' was not found with 'console_wrapper_windows.windows.editor.dev.x86_64.obj' or at 'C:\Projects\Godot\godot\bin\vc140.pdb'; linking object as if no debug info
LINK : error LNK1218: warning treated as error; no output file generated
scons: *** [bin\godot.windows.editor.dev.x86_64.console.exe] Error 4099

A simple workaround is to edit the SConstruct file by removing /WX:

if env["werror"]:
            env.Append(CCFLAGS=["/WX"])
            # env.Append(LINKFLAGS=["/WX"])

[anvilfolk]

I had this error exactly. I also cleaned everything I could, to no avail. As far as I could tell, there were no .obj files anywhere.

It's a few days later and at least one restart and I tried recompiling and just got this (without a newline between errors):

platform\windows\joypad_windows.cpp: fatal error C1041: cannot open program database 'C:\dev\godot\vc140.pdb'; if multiple CL.EXE write to the same .PDB file, please use /FSplatform\windows\vulkan_context_win.cpp: fatal error C1041: cannot open program database 'C:\dev\godot\vc140.pdb'; if multiple CL.EXE write to the same .PDB file, please use /FS

Then recompiled again and it worked.

Now I --cleaned it once more, tried recompiling and I'm back to:

LINK : error LNK1218: warning treated as error; no output file generated
scons: *** [bin\godot.windows.editor.dev.x86_64.console.exe] Error 4099

Recompiling several times does seem to be succeeding now, after a series of the errors above.

So I can see multiple things potentially being a problem:

• Something doesn't get cleaned up until a restart
• It's a spurious issue caused by multi-threaded compilation creating an invalid vc140.pdb, as indicated by the two errors above not having a newline between them (two threads writing to console a the same time?). We should test using -j1.
• Something else entirely that is only explained by dark magic

[lawnjelly]

Sounds like it does indeed needs the /fs option (force synchronous PDB writes), as the error messages suggests.
https://learn.microsoft.com/en-us/cpp/build/reference/fs-force-synchronous-pdb-writes?view=msvc-170

It could be e.g. a timing error with multiple cl.exe trying to write to the same PDB at the same time, and the timing will have changed without incremental linking.

[bruvzg]

Sounds like it does indeed needs the /fs option (force synchronous PDB writes), as the error messages suggests.

We do already set it, it's useless. The error seems to be from the linker not form cl.exe.

[akien-mga]

Cherry-picked for 3.6.

[akien-mga]

Cherry-picked for 3.5.3.

[YuriSizov]

Cherry-picked for 4.1.2.