teach ei_x_format to handle unary - and +

Teach the format string parser used for ei_x_format() and
ei_x_format_wo_ver() about unary negative and positive operators on
numbers. Previously, passing a negative numeric constant or a positive
numeric constant with an explicit leading plus sign within the format
string would cause these functions to fail.

Augment the format_wo_ver unit test in the ei_format suite with a
regression test for these cases.

An easy way to reproduce the problem is to use erl_call:

erl_call -s foo@bar -a 'erlang list_to_integer [-1]'

Without this change, erl_call fails with a -1 exit status. With this
change, it properly prints "-1".

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/erl_interface/src/misc/ei_format.c b/lib/erl_interface/src/misc/ei_format.c
index 08235d0ebe..b35421d4b2 100644
--- a/lib/erl_interface/src/misc/ei_format.c
+++ b/lib/erl_interface/src/misc/ei_format.c
@@ -106,6 +106,8 @@ static int eiformat(const char** fmt, union arg** args, ei_x_buff* x)
     default:
 	if (isdigit((int)*p))
 	    res = pdigit(&p, x);
+	else if ((*p == '-' || *p == '+') && isdigit((int)*(p+1)))
+	    res = pdigit(&p, x);
 	else if (islower((int)*p))
 	    res = patom(&p, x);
 	else
@@ -149,6 +151,8 @@ static int pdigit(const char** fmt, ei_x_buff* x)
     double d;
     long l;
 
+    if (**fmt == '-' || **fmt == '+')
+	(*fmt)++;
     for (;;) {
 	c = *(*fmt)++;
 	if (isdigit((int)c))