On 6/15/2020 12:21 PM, Josh Thompson wrote:
> We recently noticed a change in double quote (") handling that is causing a
> command we issue to fail.  The command is:
[...]
> 3.1.4:
> $ cmd.exe /c "echo \""
> "
> 
> 3.1.5:
> $ cmd.exe /c "echo \""
> \"

I can confirm this change in behavior, and I thought it would be completely 
trivial to do a bisection to find the commit that caused it.  Unfortunately, it 
seems that the issue is somehow tied up with the fact that the toolchain used 
for building the cygwin package was upgraded shortly after the release of 3.1.4.

An attempt to rebuild 3.1.4 with the current toolchain fails because of some 
gcc/binutils changes.  So I applied the attached patches, which were applied to 
the Cygwin git master shortly after the release of 3.1.4, in order to make the 
build succeed.

After installing the rebuilt 3.1.4, however, the cmd.exe call above exhibits the 
"3.1.5" behavior rather than the "3.1.4" behavior.  I can't see anything in the 
patches that would explain this.  I thought maybe it was a compiler optimization 
problem, but rebuilding without optimization doesn't change anything.

I'm stumped.

Ken