Add link_deps field

In some cases, the linking step requires some dependencies. For example,
passing a version script to the linker. The new `(link_deps)` field
uses the dependency DSL already used in other places.

Closes #852

Signed-off-by: Etienne Millon <etienne@cryptosense.com>

CHANGES.md

@@ -75,6 +75,9 @@ next
 * Allow setting environment variables in `findlib.conf` for cross compilation
   contexts. (#733, @rgrinberg)
 
+- Add a `link_deps` field to executables, to specify link-time dependencies
+  like version scripts. (#879, fix #852, @emillon)
+
 1.0+beta20 (10/04/2018)
 -----------------------
 

doc/jbuild.rst

@@ -248,6 +248,10 @@ Executables can also be linked as object or shared object files. See
 - ``(link_flags <flags>)`` specifies additional flags to pass to the linker.
   This field supports ``(:include ...)`` forms
 
+- ``(link_deps (<deps-conf list>))`` specifies the dependencies used only by the
+  linker, for example when using a version script. See the `Dependency
+  specification`_ section for more details.
+
 - ``(modules <modules>)`` specifies which modules in the current directory
   Jbuilder should consider when building this executable. Modules not listed
   here will be ignored and cannot be used inside the executable described by

src/gen_rules.ml

@@ -857,7 +857,11 @@ module Gen(P : Install_rules.Params) = struct
     in
 
     let flags = SC.ocaml_flags sctx ~scope ~dir exes.buildable in
+    let link_deps =
+      SC.Deps.interpret sctx ~scope ~dir exes.link_deps
+    in
     let link_flags =
+      link_deps >>^ ignore >>>
       SC.expand_and_eval_set sctx exes.link_flags
         ~scope
         ~dir

src/jbuild.ml

@@ -874,6 +874,7 @@ module Executables = struct
   type t =
     { names      : (Loc.t * string) list
     ; link_flags : Ordered_set_lang.Unexpanded.t
+    ; link_deps  : Dep_conf.t list
     ; modes      : Link_mode.Set.t
     ; buildable  : Buildable.t
     }
@@ -887,6 +888,7 @@ module Executables = struct
        field "link_executables" bool ~default:true >>= fun _ ->
        return ())
     >>= fun () ->
+    field "link_deps" (list Dep_conf.t) ~default:[] >>= fun link_deps ->
     field_oslu "link_flags" >>= fun link_flags ->
     field "modes" Link_mode.Set.t ~default:Link_mode.Set.default
     >>= fun modes ->
@@ -902,6 +904,7 @@ module Executables = struct
     let t =
       { names
       ; link_flags
+      ; link_deps
       ; modes
       ; buildable
       }

src/jbuild.mli

@@ -256,10 +256,11 @@ module Executables : sig
   end
 
   type t =
-    { names            : (Loc.t * string) list
-    ; link_flags       : Ordered_set_lang.Unexpanded.t
-    ; modes            : Link_mode.Set.t
-    ; buildable        : Buildable.t
+    { names      : (Loc.t * string) list
+    ; link_flags : Ordered_set_lang.Unexpanded.t
+    ; link_deps  : Dep_conf.t list
+    ; modes      : Link_mode.Set.t
+    ; buildable  : Buildable.t
     }
 end
 

test/blackbox-tests/dune.inc

@@ -330,6 +330,14 @@
     test-cases/lib-available
     (progn (run ${exe:cram.exe} -test run.t) (diff? run.t run.t.corrected))))))
 
+(alias
+ ((name link-deps)
+  (deps ((package dune) (files_recursively_in test-cases/link-deps)))
+  (action
+   (chdir
+    test-cases/link-deps
+    (progn (run ${exe:cram.exe} -test run.t) (diff? run.t run.t.corrected))))))
+
 (alias
  ((name loop)
   (deps ((package dune) (files_recursively_in test-cases/loop)))
@@ -592,6 +600,7 @@
     (alias installable-dup-private-libs)
     (alias intf-only)
     (alias lib-available)
+    (alias link-deps)
     (alias loop)
     (alias menhir)
     (alias merlin-tests)
@@ -656,6 +665,7 @@
     (alias installable-dup-private-libs)
     (alias intf-only)
     (alias lib-available)
+    (alias link-deps)
     (alias loop)
     (alias merlin-tests)
     (alias meta-gen)

test/blackbox-tests/test-cases/link-deps/dune

@@ -0,0 +1,11 @@
+(alias
+  ((name message)
+   (deps (.link_deps.eobjs/link_deps.cmo))
+   (action (echo "link\n"))
+   ))
+
+(executable
+  ((name link_deps)
+   (link_deps ((alias message)))
+   )
+  )

test/blackbox-tests/test-cases/link-deps/dune-project

@@ -0,0 +1 @@
+(lang dune 1.0)

test/blackbox-tests/test-cases/link-deps/run.t

@@ -0,0 +1,11 @@
+It is possible to add link-time dependencies.
+
+In particular, these can depend on the result of the compilation (like a .cmo
+file) and be created just before linking.
+
+  $ dune build --display short link_deps.exe
+      ocamldep link_deps.ml.d
+        ocamlc .link_deps.eobjs/link_deps.{cmi,cmo,cmt}
+  link
+      ocamlopt .link_deps.eobjs/link_deps.{cmx,o}
+      ocamlopt link_deps.exe