How can I speed up MinGW-w64's extremely slow C++ compilation/linking?
Compiling a trivial "Hello World" program:
#include <iostream>
int main()
{
std::cout << "hello world" << std::endl;
}
...takes 3 minutes(!) on this otherwise-unloaded Windows 10 machine (i7-6700, 32GB of RAM, decent SATA SSD):
> ptime.exe g++ main.cpp
ptime 1.0 for Win32, Freeware - http://www.pc-tools.net/
Copyright(C) 2002, Jem Berkes <jberkes@pc-tools.net>
=== g++ main.cpp ===
Execution time: 180.488 s
Process Explorer shows the g++ process tree bottoming out in ld.exe which doesn't use any appreciable CPU or I/O for the duration.
Running the g++ process tree through API Monitor shows there are three unusually long syscalls in ld.exe: two NtCreateFile()s and a NtOpenFile(), each operating on a.exe and taking 60 seconds apiece.
The slowness only happens when using the default a.exe output; g++ -o foo.exe main.cpp takes 2 seconds, tops.
"Well don't use a.exe as an output name then!" isn't really a solution since this behavior causes CMake to take ages doing compiler feature detection.
GCC toolchain versions:
>g++ --version
g++ (x86_64-posix-seh-rev0, Built by MinGW-W64 project) 8.1.0
>ld --version
GNU ld (GNU Binutils) 2.30
Given that I couldn't repro the problem in a clean Windows 10 VM and the dependence on the output filename led me down the path of anti-virus/anti-malware interference.
fltmc instances listed several possible filesystem filter drivers; guess-n-check narrowed it down to two of Carbon Black's: carbonblackk & ParityDriver.
Using Regedit to disable them via setting Start to 0x4 ("Disabled", 0x2 == Automatic, 0x3 == Manual) in these two registry keys followed by a reboot fixed the slowness: