Failure to compile FFI-readline example on nix.

[locallycompact]

Hi. I get this error when I try to build the FFI-readline example.

[I] lc@aiur ~/S/g/i/I/s/FFI-readline (master) [127]> nix-shell -p readline --command 'idris2 --build readline.ipkg'
make: Entering directory '/home/lc/Source/github.com/idris-lang/Idris2/samples/FFI-readline/readline_glue'
gcc -Wall  -fPIC   -c -o idris_readline.o idris_readline.c
In file included from /nix/store/ahsfc5f18l7y25ykp10cp6wfqcp5qwvq-readline-6.3p08-dev/include/readline/readline.h:35,
                 from idris_readline.c:1:
/nix/store/ahsfc5f18l7y25ykp10cp6wfqcp5qwvq-readline-6.3p08-dev/include/readline/rltypedefs.h:71:28: error: unknown type name ‘FILE’
   71 | typedef int rl_getc_func_t PARAMS((FILE *));
      |                            ^~~~~~
In file included from /nix/store/ahsfc5f18l7y25ykp10cp6wfqcp5qwvq-readline-6.3p08-dev/include/readline/readline.h:36,
                 from idris_readline.c:1:
/nix/store/ahsfc5f18l7y25ykp10cp6wfqcp5qwvq-readline-6.3p08-dev/include/readline/rltypedefs.h:1:1: note: ‘FILE’ is defined in header ‘<stdio.h>’; did you forget to ‘#include <stdio.h>’?
  +++ |+#include <stdio.h>

[gallais]

We don't seem to have continuous integration for the content of samples/. Still, I was able to compile the file on ubuntu after installing libreadline-dev. Could it be that this is an upstream issue in the readline package nix uses?

[locallycompact]

That seems likely.

[claymager]

Looks like it's in readline. The manpages imply you have to manually #include <stdio.h> first. At least Arch and NixOS have this issue, so maybe Ubuntu modifies libreadline-dev?

Adding that line allows me to build in NixOS.

[gallais]

Okay I've tried adding this extra line too and it does not break the build on Ubuntu AFAICT. I'll be happy to merge a PR including that line & adding samples to the CI.

[ProofOfKeags]

Given that it seems this was an issue in the nix repo, maybe it is worth revisiting whether this is still an issue over a year later.