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".

2 files changed, 2 insertions, 2 deletions

diff --git a/lib/erl_interface/test/ei_format_SUITE.erl b/lib/erl_interface/test/ei_format_SUITE.erl
index 7871f07ae9..cbe9fa52d7 100644
--- a/lib/erl_interface/test/ei_format_SUITE.erl
+++ b/lib/erl_interface/test/ei_format_SUITE.erl
@@ -155,7 +155,7 @@ format_wo_ver(suite) -> [];
 format_wo_ver(Config) when is_list(Config) ->
     ?line P = runner:start(?format_wo_ver),
 
-    ?line {term, [{a, "b"}, {c, 10}]} = get_term(P),
+    ?line {term, [-1, 2, {a, "b"}, {c, 10}]} = get_term(P),
 
     ?line runner:recv_eot(P),
     ok.
diff --git a/lib/erl_interface/test/ei_format_SUITE_data/ei_format_test.c b/lib/erl_interface/test/ei_format_SUITE_data/ei_format_test.c
index a969ded3dc..ecdce402f5 100644
--- a/lib/erl_interface/test/ei_format_SUITE_data/ei_format_test.c
+++ b/lib/erl_interface/test/ei_format_SUITE_data/ei_format_test.c
@@ -176,7 +176,7 @@ TESTCASE(format_wo_ver) {
     ei_x_buff x;
     
     ei_x_new (&x);
-    ei_x_format(&x, "[{~a,~s},{~a,~i}]", "a", "b", "c", 10);
+    ei_x_format(&x, "[-1, +2, {~a,~s},{~a,~i}]", "a", "b", "c", 10);
     send_bin_term(&x);
 
     free(x.buff);