[fpc-pascal] Search path order for fpc.cfg

[Michael Van Canneyt]

On Sat, 11 Apr 2020, Jonas Maebe wrote:

> On 11/04/2020 08:24, Michael Van Canneyt wrote:
>> it is not done on unices to search in the binary directory for config
>> files. That's a windows thing.
>
> And the main reason for this is that "the" compiler binary does not
> necessarily exist. The most obvious case is a hard link: in this case, a
> single file exists in multiple locations on the file system. A program
> file can also be moved while it was executing.
>
> Even if you ignore the above cases and only care about the directory in
> which the binary was found when it was started, then there is still the
> issue that not all Unix systems provide you with that information. E.g.
> on Darwin/macOS, if you just type "ppcx64", then the "full path" to the
> binary that the program gets is "ppcx64" and you have no idea where it's
> located. You can use some heuristics like looking in the path, but this
> is fragile and might possibly even be used for attacks (it is probably
> possible to specify a different PATH environment variable to the child
> process than the one used to originally find it).
>
> This is also the reason why most Unix programs have there installation
> directory compiled into the binary, and why you often have to specify it
> already when building the program (rather than only when installing it).
> FPC does not do that due to its DOS and OS/2 heritage, but it's not
> something we should extend.

In short: 
the installer should write a 'correct' config file, without tricks
like relative paths.

Many unix programs that can be installed 'anywhere' require you to set
environment variables in order to find where you installed it.

Michael.