(zilch lang rust cargo): parse cfg values at runtime

lang/rust/cfg-fetch.rs

@@ -0,0 +1,10 @@
+use std::{env::var_os, fs::{create_dir, File}, os::unix::process::CommandExt, process::Command};
+
+fn main() {
+    Err(
+        Command::new(var_os("rustc").unwrap())
+        .arg("--print=cfg")
+        .stdout(File::create(var_os("out").unwrap()).unwrap())
+        .exec())
+    .unwrap()
+}

lang/rust/default.nix

@@ -15,5 +15,6 @@
   ];
   overrides.preBuild = ''
     (cat buildrs-runner.rs; printf '\0') | xxd -i -n runner_source > runner_source.h
+    (cat cfg-fetch.rs; printf '\0') | xxd -i -n cfgfetch_source > cfgfetch_source.h
   '';
 }

lang/rust/src/cargo.sld

@@ -9,6 +9,7 @@
   (chicken foreign)
   (srfi 4) (srfi 128) (srfi 146) (srfi 152) (srfi 207)
   (zilch lang rust registry) (zilch lang rust) (zilch lang rust cfg)
+  (zilch lang rust cfg)
   (zilch lang go vfs))
 
  (export
@@ -36,6 +37,8 @@
   <cargo-workspace> make-cargo-workspace cargo-workspace?
   cargo-workspace-members cargo-workspace-exclude cargo-workspace-dependencies
 
+  cfg-values
+
   parse-cargo-toml)
 
  (begin
@@ -182,45 +185,28 @@
        (cargo-workspace-exclude entry)
        (cargo-workspace-dependencies entry)))
   
-   ; TODO(puck): aaaa
+   (foreign-declare "#include \"cfgfetch_source.h\"")
+   (define cfgfetch-bin
+     (cdar
+       (call-rustc
+         (zfile (foreign-value "cfgfetch_source" nonnull-c-string)) '()
+         #:codegen-flags (cons "linker" (force linker))
+         #:crate-type 'bin
+         #:crate-name "cfgfetch"
+         #:edition "2021"
+         #:emits '(#:link #t))))
+
    (define cfg-target "x86_64-unknown-linux-gnu")
+   (define (read-cfg-value port rest)
+     (define line (read-line port))
+     (if (eof-object? line)
+       rest
+       (let* ((line (cfg-parse line)))
+         (read-cfg-value port (cons (cdr line) rest)))))
+
    (define cfg-values
-     '(( "debug_assertions" . #f)
-       ( "fmt_debug" . "full")
-       ( "overflow_checks" . #f)
-       ( "panic" . "unwind")
-       ( "relocation_model" . "pic")
-       ( "target_abi" . "")
-       ( "target_arch" . "x86_64")
-       ( "target_endian" . "little")
-       ( "target_env" . "gnu")
-       ( "target_family" . "unix")
-       ( "target_feature" . "fxsr")
-       ( "target_feature" . "sse")
-       ( "target_feature" . "sse2")
-       ( "target_has_atomic" . #f)
-       ( "target_has_atomic" . "16")
-       ( "target_has_atomic" . "32")
-       ( "target_has_atomic" . "64")
-       ( "target_has_atomic" . "8")
-       ( "target_has_atomic" . "ptr")
-       ( "target_has_atomic_equal_alignment" . "16")
-       ( "target_has_atomic_equal_alignment" . "32")
-       ( "target_has_atomic_equal_alignment" . "64")
-       ( "target_has_atomic_equal_alignment" . "8")
-       ( "target_has_atomic_equal_alignment" . "ptr")
-       ( "target_has_atomic_load_store" . #f)
-       ( "target_has_atomic_load_store" . "16")
-       ( "target_has_atomic_load_store" . "32")
-       ( "target_has_atomic_load_store" . "64")
-       ( "target_has_atomic_load_store" . "8")
-       ( "target_has_atomic_load_store" . "ptr")
-       ( "target_os" . "linux")
-       ( "target_pointer_width" . "64")
-       ( "target_thread_local" . #f)
-       ( "target_vendor" . "unknown")
-       ( "ub_checks" . #f)
-       ( "unix" . #f)))
+     (let ((vals (cdar (store-path-for-ca-drv* "cfg-values" "x86_64-linux" #~(#$cfgfetch-bin) #~(("rustc" . ,(string-append #$rustc "/bin/rustc"))) '("out")))))
+       (call-with-port (store-path-open vals) (lambda (p) (read-cfg-value p '())))))
 
    (define (cratify-name name)
     ; NOTE! string-map _has_ to return a char. non-chars are mistreated and cause memory corruption.