From fc92c2d8942cf466aa6dbc422f2e798801b18408 Mon Sep 17 00:00:00 2001
From: Philipp Stephani <phst@google.com>
Date: Sun, 5 Jan 2020 16:05:14 +0100
Subject: [PATCH] Also print function data when printing module functions.
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This is especially useful in cases where modules only use a single
entry point and use the data to dispatch to the actual function.  Such
a design is common for languages such as Go and C++.

* src/emacs-module.c (module_function_data): New function.

* src/print.c (print_vectorlike): Use it to print module function data
if not NULL.
(print_object): Adapt size of buffer.

* test/data/emacs-module/mod-test.c (emacs_module_init): Pass some
non-NULL data to ‘mod-test-sum’.
(Fmod_test_sum): Check that correct data is passed through.

* test/src/emacs-module-tests.el (mod-test-sum-test)
(module-function-object): Adapt unit tests.
---
 src/emacs-module.c                |  6 ++++++
 src/lisp.h                        |  1 +
 src/print.c                       | 18 ++++++++++++++++--
 test/data/emacs-module/mod-test.c |  5 ++++-
 test/src/emacs-module-tests.el    |  6 ++++--
 5 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/src/emacs-module.c b/src/emacs-module.c
index 3855a33f254..f40ca931fa9 100644
--- a/src/emacs-module.c
+++ b/src/emacs-module.c
@@ -1098,6 +1098,12 @@ module_function_address (const struct Lisp_Module_Function *function)
   return (module_funcptr) function->subr;
 }
 
+void *
+module_function_data (const struct Lisp_Module_Function *function)
+{
+  return function->data;
+}
+
 
 /* Helper functions.  */
 
diff --git a/src/lisp.h b/src/lisp.h
index 9be7bfec5c0..e1bbb53ad49 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4245,6 +4245,7 @@ extern Lisp_Object module_function_documentation
   (struct Lisp_Module_Function const *);
 extern module_funcptr module_function_address
   (struct Lisp_Module_Function const *);
+extern void *module_function_data (const struct Lisp_Module_Function *);
 extern void module_finalize_function (const struct Lisp_Module_Function *);
 extern void mark_modules (void);
 extern void init_module_assertions (bool);
diff --git a/src/print.c b/src/print.c
index 425b0dc4ee3..b373aaf6551 100644
--- a/src/print.c
+++ b/src/print.c
@@ -1796,7 +1796,8 @@ print_vectorlike (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag,
     case PVEC_MODULE_FUNCTION:
       {
 	print_c_string ("#<module function ", printcharfun);
-        module_funcptr ptr = module_function_address (XMODULE_FUNCTION (obj));
+        const struct Lisp_Module_Function *function = XMODULE_FUNCTION (obj);
+        module_funcptr ptr = module_function_address (function);
 	char const *file;
 	char const *symbol;
 	dynlib_addr (ptr, &file, &symbol);
@@ -1815,6 +1816,19 @@ print_vectorlike (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag,
 	else
 	  print_c_string (symbol, printcharfun);
 
+        void *data = module_function_data (function);
+        if (data != NULL)
+          {
+	    uintptr_t ui = (uintptr_t) data;
+
+	    /* In theory this assignment could lose info on pre-C99
+	       hosts, but in practice it doesn't.  */
+	    uintmax_t up = ui;
+
+	    int len = sprintf (buf, " with data 0x%"PRIxMAX, up);
+	    strout (buf, len, len, printcharfun);
+          }
+
 	if (file != NULL)
 	  {
 	    print_c_string (" from ", printcharfun);
@@ -1838,7 +1852,7 @@ print_object (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
 {
   char buf[max (sizeof "from..to..in " + 2 * INT_STRLEN_BOUND (EMACS_INT),
 		max (sizeof " . #" + INT_STRLEN_BOUND (intmax_t),
-		     max ((sizeof "at 0x"
+		     max ((sizeof " with data 0x"
 			   + (sizeof (uintmax_t) * CHAR_BIT + 4 - 1) / 4),
 			  40)))];
   current_thread->stack_top = buf;
diff --git a/test/data/emacs-module/mod-test.c b/test/data/emacs-module/mod-test.c
index 1a0a879a1bc..ec6948921f2 100644
--- a/test/data/emacs-module/mod-test.c
+++ b/test/data/emacs-module/mod-test.c
@@ -24,6 +24,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #include <errno.h>
 #include <limits.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -86,6 +87,7 @@ static emacs_value
 Fmod_test_sum (emacs_env *env, ptrdiff_t nargs, emacs_value args[], void *data)
 {
   assert (nargs == 2);
+  assert ((uintptr_t) data == 0x1234);
 
   intmax_t a = env->extract_integer (env, args[0]);
   intmax_t b = env->extract_integer (env, args[1]);
@@ -587,7 +589,8 @@ emacs_module_init (struct emacs_runtime *ert)
 		 env->make_function (env, amin, amax, csym, doc, data))
 
   DEFUN ("mod-test-return-t", Fmod_test_return_t, 1, 1, NULL, NULL);
-  DEFUN ("mod-test-sum", Fmod_test_sum, 2, 2, "Return A + B\n\n(fn a b)", NULL);
+  DEFUN ("mod-test-sum", Fmod_test_sum, 2, 2, "Return A + B\n\n(fn a b)",
+         (void *) (uintptr_t) 0x1234);
   DEFUN ("mod-test-signal", Fmod_test_signal, 0, 0, NULL, NULL);
   DEFUN ("mod-test-throw", Fmod_test_throw, 0, 0, NULL, NULL);
   DEFUN ("mod-test-non-local-exit-funcall", Fmod_test_non_local_exit_funcall,
diff --git a/test/src/emacs-module-tests.el b/test/src/emacs-module-tests.el
index c61abfdf683..48d2e86a605 100644
--- a/test/src/emacs-module-tests.el
+++ b/test/src/emacs-module-tests.el
@@ -60,8 +60,9 @@
     (should (eq 0
                 (string-match
                  (concat "#<module function "
-                         "\\(at \\(0x\\)?[[:xdigit:]]+\\( from .*\\)?"
-                         "\\|Fmod_test_sum from .*\\)>")
+                         "\\(at \\(0x\\)?[[:xdigit:]]+ "
+                         "with data 0x1234\\( from .*\\)?"
+                         "\\|Fmod_test_sum with data 0x1234 from .*\\)>")
                  (prin1-to-string (nth 1 descr)))))
     (should (= (nth 2 descr) 3)))
   (should-error (mod-test-sum "1" 2) :type 'wrong-type-argument)
@@ -97,6 +98,7 @@ changes."
              (rx bos "#<module function "
                  (or "Fmod_test_sum"
                      (and "at 0x" (+ hex-digit)))
+                 " with data 0x1234"
                  (? " from " (* nonl) "mod-test" (* nonl) )
                  ">" eos)
              (prin1-to-string func)))))
-- 
2.39.2