I've just pushed a fix which enables me to successfully build GCC4TI @ HEAD of the "next" branch with GCC 10, 8, 6 and 4.9. You can pull the changes from the GCC4TI repository, or re-clone it entirely if you prefer, and retry building

Yeah... That's the problem. Yosemite is really old (From a mac standpoint) and no gcc builds. Apple moves really fast with dropping support, and Homebrew is forced to follow them. I only have clang, but I'll try random packages in the hopes that one will work.

Okay... I manually compiled GCC6, removed the symlinks for to clang, and reran the install script. I got errors again. Mostly problems with the enums.

I'd need to have access to a similar system to try and debug whatever build issues you're experiencing.

I can easily spring up Linux chroots or full-blown distros, even for some non-x86(_64) archs, I do have access to several Windows versions... but MacOS X is generally harder to emulate, seldom provided in interactive cloud environments (let alone in the version that you're using), and Apple hardware is expensive (despite being fragile, in my experience, but that's off-topic)...

Virtualbox has an option to emulate Mac hardware. It doesn't support the latest ones, though.

This is kind of a necropost, but I think it has some value.

For all the users of *nix operating systems, you have two options:

A) Do what I tried to do, and install an ancient version of GCC. It probably works on linux, but Apple's bash is likely modified (And so would be incompatible with GNU bash), so you'll get all kinds of build errors.

B) Install WINE, download the win32 installer, and double click it. The IDE works perfectly with WINE, the compiler works perfectly as well, and you get all the other windows only tools... Again, perfect. It's also quite easy to create small scripts to run the executables, then put them in a folder and add them to your path.

It's lucky that its 32-bit...

Anyway,
Thank you @Lionel Debroux for your help!

Far from being perfect, using the Win32 installer and leaving it at that is actually a very bad thing to do: this way, you only get a severely outdated version, even though yes, that is the latest release, I know...
Making a new release for Windows is a lot of work which requires usage of a native Windows host and commercial software of which I have no recent version: recompiling the IDE and the Windows tigcc using Delphi, recompiling the HTML help files to CHM using hhc, regenerating the code completion definitions for the Delphi IDE, generating an automated installer, and whatever else I forgot.

Besides the IDE with well-documented shortcomings, you don't get much in the way of other Windows-only tools.

However, I have published the build definitions for creating an overlay ZIP, which makes it possible to get most non-documentation fixes and improvements. Such an overlay ZIP is even publicly accessible, just not at a really officially documented location. I'll check later which is the date of that ZIP, and probably post a link here
EDIT: https://tiplanet.org/beta/gcc4tis.tar.bz2 , built using older tools.

Well, I found something interesting. Compilation works from the IDE but not the command line.

EDIT: I know what's happening:

The script I made (called "tigcc" to make my life easier) is sitting in a folder appended to the end of my path. The broken TIGCC executables were before it. After I removed them, it works fine.

That's not what happened for you, but FTR, in general, that's precisely one of the well-documented shortcomings of the IDE, with its weird "virtual folders" system.