Cygwin 3.3.1 tgmath.h plus log10() gives "error: no matching function for type-generic call"

[Ed .]

Dear Cygwin folks,

As shown in this run of PDL (Perl Data Language)’s CI, our new use of tgmath.h is causing a problem with log10:

https://github.com/PDLPorters/pdl/runs/4134966240?check_suite_focus=true

The error is:

In file included from pp-log10.c:56:
1744<https://github.com/PDLPorters/pdl/runs/4134966240?check_suite_focus=true#step:11:1744>ops.pd: In function ‘pdl_log10_readdata’:
1745<https://github.com/PDLPorters/pdl/runs/4134966240?check_suite_focus=true#step:11:1745>ops.pd:321:35: error: no matching function for type-generic call

The line numbers aren’t directly meaningful due to my enthusiastic use of #line in the project, but I believe the error is triggered by calling log10() with an unsigned char. This appears to work fine on GCC on Linux (and Windows, and with clang on MacOS).

I tried for some time to find out which versions of GCC, glibc etc Cygwin 3.3.1 includes, and was unsuccessful. The best I could see was that the Choco package seems to also include “[Cygwin] 11 install gcc-core 11.2.0-1”.

Any pointers (ha!) gratefully received.

Best regards,
Ed