expr: allow existing multiple argument support with --compat

Some users may not be ready to immediately move to the single-argument
expr, so provide a --compat option to configure to support the
previous behaviour as a transition strategy.

Signed-off-by: Steve Bennett <steveb@workware.net.au>

3 files changed, 29 insertions, 4 deletions

diff --git a/auto.def b/auto.def
index 8ab5022..3f2f5a0 100644
--- a/auto.def
+++ b/auto.def
@@ -21,6 +21,7 @@ options {
     maintainer      => {Enable the [debug] command and JimPanic}
     full            => "Enable some optional features: ipv6, ssl, math, utf8, and some extensions (see --extinfo)"
     allextmod       => "Enable all non-default extensions as modules if prerequisites are found"
+    compat          => "Enable some backward compatibility behaviour"
     extinfo         => "Show information about available extensions"
     with-jim-shared shared => "Build a shared library instead of a static library"
     jim-regexp=1    => "Prefer POSIX regex if over the the built-in (Tcl-compatible) regex"
@@ -432,6 +433,10 @@ if {[opt-bool references]} {
     msg-result "Enabling references"
     define JIM_REFERENCES
 }
+if {[opt-bool compat]} {
+    msg-result "Enabling compatibility mode"
+    define JIM_COMPAT
+}
 if {[opt-bool shared with-jim-shared]} {
     msg-result "Building shared library"
 } else {
diff --git a/jim.c b/jim.c
index 64f47bd..cfc0f8f 100644
--- a/jim.c
+++ b/jim.c
@@ -13598,11 +13598,31 @@ static int Jim_UplevelCoreCommand(Jim_Interp *interp, int argc, Jim_Obj *const *
 /* [expr] */
 static int Jim_ExprCoreCommand(Jim_Interp *interp, int argc, Jim_Obj *const *argv)
 {
+    int retcode;
+
     if (argc == 2) {
-        return Jim_EvalExpression(interp, argv[1]);
+        retcode = Jim_EvalExpression(interp, argv[1]);
     }
-    Jim_WrongNumArgs(interp, 1, argv, "expression");
-    return JIM_ERR;
+#ifndef JIM_COMPAT
+    else {
+        Jim_WrongNumArgs(interp, 1, argv, "expression");
+        retcode = JIM_ERR;
+    }
+#else
+    else if (argc > 2) {
+        Jim_Obj *objPtr;
+
+        objPtr = Jim_ConcatObj(interp, argc - 1, argv + 1);
+        Jim_IncrRefCount(objPtr);
+        retcode = Jim_EvalExpression(interp, objPtr);
+        Jim_DecrRefCount(interp, objPtr);
+    }
+    else {
+        Jim_WrongNumArgs(interp, 1, argv, "expression ?...?");
+        return JIM_ERR;
+    }
+#endif
+    return retcode;
 }
 
 /* [break] */
diff --git a/jim_tcl.txt b/jim_tcl.txt
index aea64f4..49972b7 100644
--- a/jim_tcl.txt
+++ b/jim_tcl.txt
@@ -65,7 +65,7 @@ Changes since 0.80
 8. `lsort -index` now supports multiple indices
 9. Add support for `lsort -stride`
 10. `open` now supports POSIX-style access arguments
-11. TIP 526, `expr` now only allows a single argument
+11. TIP 526, `expr` now only allows a single argument (unless --compat is enabled)
 
 Changes between 0.79 and 0.80
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~