Merge pull request #4088 from MisterDA/configurator-c-libraries

Always link the c_libraries in the configurator build command

CHANGES.md

@@ -7,6 +7,9 @@
 - Fixed memory blow up introduced in 2.8.0 (#4144, fixes #4134,
   @jeremiedimino)
 
+- Configurator: always link the C libraries in the build command
+  (#4088, @MisterDA).
+
 2.8.1 (14/01/2021)
 ------------------
 

otherlibs/configurator/src/v1.ml

@@ -12,6 +12,7 @@ type t =
   ; c_compiler : string
   ; stdlib_dir : string
   ; ccomp_type : string
+  ; c_libraries : string list
   ; ocamlc_config : Ocaml_config.Vars.t
   ; ocamlc_config_cmd : string
   }
@@ -310,16 +311,21 @@ let read_dot_dune_configurator_file ~build_dir =
 
 let fill_in_fields_that_depends_on_ocamlc_config t =
   let get = ocaml_config_var_exn t in
-  let c_compiler =
+  let get_flags var =
+    get var |> String.trim |> Flags.extract_blank_separated_words
+  in
+  let c_compiler, c_libraries =
     match Ocaml_config.Vars.find t.ocamlc_config "c_compiler" with
-    | Some c_comp -> c_comp ^ " " ^ get "ocamlc_cflags"
-    | None -> get "bytecomp_c_compiler"
+    | Some c_comp ->
+      (c_comp ^ " " ^ get "ocamlc_cflags", get_flags "native_c_libraries")
+    | None -> (get "bytecomp_c_compiler", get_flags "bytecomp_c_libraries")
   in
   { t with
     ext_obj = get "ext_obj"
   ; c_compiler
   ; stdlib_dir = get "standard_library"
   ; ccomp_type = get "ccomp_type"
+  ; c_libraries
   }
 
 let create_from_inside_dune ~dest_dir ~log ~build_dir ~name =
@@ -344,6 +350,7 @@ let create_from_inside_dune ~dest_dir ~log ~build_dir ~name =
     ; c_compiler = ""
     ; stdlib_dir = ""
     ; ccomp_type = ""
+    ; c_libraries = []
     }
 
 let create ?dest_dir ?ocamlc ?(log = ignore) name =
@@ -372,6 +379,7 @@ let create ?dest_dir ?ocamlc ?(log = ignore) name =
       ; c_compiler = ""
       ; stdlib_dir = ""
       ; ccomp_type = ""
+      ; c_libraries = []
       ; ocamlc_config = Ocaml_config.Vars.of_list_exn []
       ; ocamlc_config_cmd
       }
@@ -410,12 +418,13 @@ let compile_and_link_c_prog t ?(c_flags = []) ?(link_flags = []) code =
   let ok =
     if need_to_compile_and_link_separately t then
       run_ok (c_flags @ [ "-I"; t.stdlib_dir; "-c"; c_fname ])
-      && run_ok ("-o" :: exe_fname :: obj_fname :: link_flags)
+      && run_ok (("-o" :: exe_fname :: obj_fname :: t.c_libraries) @ link_flags)
     else
       run_ok
         (List.concat
            [ c_flags
            ; [ "-I"; t.stdlib_dir; "-o"; exe_fname; c_fname ]
+           ; t.c_libraries
            ; link_flags
            ])
   in
@@ -436,7 +445,9 @@ let compile_c_prog t ?(c_flags = []) code =
   let ok =
     Process.run_command_ok t ~dir
       (Process.command_args t.c_compiler
-         (c_flags @ [ "-I"; t.stdlib_dir; "-o"; obj_fname; "-c"; c_fname ]))
+         ( c_flags
+         @ "-I" :: t.stdlib_dir :: "-o" :: obj_fname :: "-c" :: c_fname
+           :: t.c_libraries ))
   in
   if ok then
     Ok obj_fname

test/blackbox-tests/test-cases/configurator-c-libraries.t/discover.ml

@@ -0,0 +1,26 @@
+module C = Configurator.V1
+
+let unix = {|
+#include <math.h>
+void *addr = &sin;
+int main(void) {
+    return 0;
+}
+|}
+
+let windows = {|
+#include <winsock2.h>
+void *addr = &gethostname;
+int main(void) {
+    return 0;
+}
+|}
+
+let main c =
+  let code = if Sys.os_type = "Win32" then windows else unix in
+  let b = C.c_test c code in
+  let f = open_out_bin "out" in
+  output_char f (if b then '1' else '0');
+  close_out f
+
+let () = C.main ~name:"configurator-c-libraries" main

test/blackbox-tests/test-cases/configurator-c-libraries.t/dune

@@ -0,0 +1,3 @@
+(executable
+ (name discover)
+ (libraries dune.configurator))

test/blackbox-tests/test-cases/configurator-c-libraries.t/dune-project

@@ -0,0 +1 @@
+(lang dune 2.8)

test/blackbox-tests/test-cases/configurator-c-libraries.t/run.t

@@ -0,0 +1,13 @@
+Test that configurator always picks the value of the `c_libraries`
+flag from `ocamlc -config`. If not, there's a failure to link a
+configuration test program that uses functions from these libraries.
+For that, we need functions outside of libc. On Unix, that would be
+`sin(3)` that requires the `-lm` flag for the math library, and on
+Windows `gethostname` that requires WinSock2 (`ws2_32.dll`).
+
+link successfully
+==================================
+
+  $ dune exec -- ./discover.exe
+  $ cat out
+  1