Relax eval as allowed by POSIX 2008.

* modules/evalparse.c (m4_evaluate): Warn, not error, on invalid
operator.  Quote expression in warning.
* modules/mpeval.c (includes): Add quotearg.h.
* doc/m4.texinfo (Eval, Improved forloop): Update tests.
* NEWS: Update to reflect 1.6 support for `?:'.

Signed-off-by: Eric Blake <ebb9@byu.net>

5 files changed, 28 insertions, 13 deletions

diff --git a/ChangeLog b/ChangeLog
index 43213844..9d1c1c85 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2008-12-24  Eric Blake  <ebb9@byu.net>
+
+	Relax eval as allowed by POSIX 2008.
+	* modules/evalparse.c (m4_evaluate): Warn, not error, on invalid
+	operator.  Quote expression in warning.
+	* modules/mpeval.c (includes): Add quotearg.h.
+	* doc/m4.texinfo (Eval, Improved forloop): Update tests.
+	* NEWS: Update to reflect 1.6 support for `?:'.
+
 2008-12-23  Eric Blake  <ebb9@byu.net>
 
 	Add debugmode(o) to control dumpdef output location.
diff --git a/NEWS b/NEWS
index 4180190d..ca4e0b0b 100644
--- a/NEWS
+++ b/NEWS
@@ -158,7 +158,7 @@ promoted to 2.0.
     first line to show the definition of the macro being expanded.
 
 *** The `eval' and `mpeval' builtins now support the following new
-    operators: `>>>', `\', `?:', and  `,'.
+    operators: `>>>', `\', and  `,'.
 
 *** The `maketemp' builtin now always warns that it is obsolete, even in GNU
     mode where it uses the same secure algorithm as `mkstemp', because of
@@ -296,6 +296,10 @@ promoted to 2.0.
    context of a macro name, rather than acting on the empty string.  This
    was already done for `define', `pushdef', `builtin', and `indir'.
 
+** Enhance the `eval' builtin to understand the `?:' operator, and
+   downgrade a failed parse due to an unknown operator from an error to a
+   warning.
+
 ** A number of portability improvements inherited from gnulib.
 
 * Noteworthy changes in Version 1.4.10b (2008-02-25) [beta]
diff --git a/doc/m4.texinfo b/doc/m4.texinfo
index 3d039f6d..c5e36dd5 100644
--- a/doc/m4.texinfo
+++ b/doc/m4.texinfo
@@ -7506,7 +7506,6 @@ precedence rules, but where older versions and some other
 implementations of @code{m4} require explicit parentheses to get the
 correct result:
 
-@comment status: 1
 @example
 eval(`1 == 2 > 0')
 @result{}1
@@ -7523,23 +7522,23 @@ eval(`(1 | 1) ^ 1')
 eval(`+ + - ~ ! ~ 0')
 @result{}1
 eval(`++0')
-@error{}m4:stdin:8: eval: invalid operator: ++0
+@error{}m4:stdin:8: Warning: eval: invalid operator: `++0'
 @result{}
 eval(`1 = 1')
-@error{}m4:stdin:9: eval: invalid operator: 1 = 1
+@error{}m4:stdin:9: Warning: eval: invalid operator: `1 = 1'
 @result{}
 eval(`0 |= 1')
-@error{}m4:stdin:10: eval: invalid operator: 0 |= 1
+@error{}m4:stdin:10: Warning: eval: invalid operator: `0 |= 1'
 @result{}
 eval(`2 || 1 / 0')
 @result{}1
 eval(`0 || 1 / 0')
-@error{}m4:stdin:12: Warning: eval: divide by zero: 0 || 1 / 0
+@error{}m4:stdin:12: Warning: eval: divide by zero: `0 || 1 / 0'
 @result{}
 eval(`0 && 1 % 0')
 @result{}0
 eval(`2 && 1 % 0')
-@error{}m4:stdin:14: Warning: eval: modulo by zero: 2 && 1 % 0
+@error{}m4:stdin:14: Warning: eval: modulo by zero: `2 && 1 % 0'
 @result{}
 @end example
 
@@ -7567,9 +7566,9 @@ eval(`2 ** 0')
 @result{}1
 eval(`0 ** 0')
 @result{}
-@error{}m4:stdin:5: Warning: eval: divide by zero: 0 ** 0
+@error{}m4:stdin:5: Warning: eval: divide by zero: `0 ** 0'
 eval(`4 ** -2')
-@error{}m4:stdin:6: Warning: eval: negative exponent: 4 ** -2
+@error{}m4:stdin:6: Warning: eval: negative exponent: `4 ** -2'
 @result{}
 eval(`2 || 4 ** -2')
 @result{}1
@@ -7632,7 +7631,7 @@ square(square(`5')` + 1')
 define(`foo', `666')
 @result{}
 eval(`foo / 6')
-@error{}m4:stdin:11: Warning: eval: bad expression: foo / 6
+@error{}m4:stdin:11: Warning: eval: bad expression: `foo / 6'
 @result{}
 eval(foo / 6)
 @result{}111
@@ -9317,7 +9316,7 @@ forloop(`', `1', `2', ` odd iterator name')
 forloop(`i', `5 + 5', `0xc', ` 0x`'eval(i, `16')')
 @result{} 0xa 0xb 0xc
 forloop(`i', `a', `b', `non-numeric bounds')
-@error{}m4:stdin:6: Warning: eval: bad input: (a) <= (b)
+@error{}m4:stdin:6: Warning: eval: bad input: `(a) <= (b)'
 @result{}
 @end example
 
diff --git a/modules/evalparse.c b/modules/evalparse.c
index 9927e13a..ac30cfe9 100644
--- a/modules/evalparse.c
+++ b/modules/evalparse.c
@@ -940,6 +940,8 @@ m4_evaluate (m4 *context, m4_obstack *obs, size_t argc, m4_macro_args *argv)
 	err = EXCESS_INPUT;
     }
 
+  if (err != NO_ERROR)
+    str = quotearg_style_mem (locale_quoting_style, str, M4ARGLEN (1));
   switch (err)
     {
     case NO_ERROR:
@@ -967,8 +969,7 @@ m4_evaluate (m4 *context, m4_obstack *obs, size_t argc, m4_macro_args *argv)
       break;
 
     case INVALID_OPERATOR:
-      /* POSIX requires an error here, unless XCU ERN 137 is approved.  */
-      m4_error (context, 0, 0, me, _("invalid operator: %s"), str);
+      m4_warn (context, 0, me, _("invalid operator: %s"), str);
       break;
 
     case DIVIDE_ZERO:
diff --git a/modules/mpeval.c b/modules/mpeval.c
index 63cd56a4..2d63d6ec 100644
--- a/modules/mpeval.c
+++ b/modules/mpeval.c
@@ -32,6 +32,8 @@
 #  include <gmp.h>
 #endif
 
+#include "quotearg.h"
+
 /* Rename exported symbols for dlpreload()ing.  */
 #define m4_builtin_table	mpeval_LTX_m4_builtin_table
 #define m4_macro_table		mpeval_LTX_m4_macro_table