dc: execute shouldn't pop if stack head is not a string

This matches the behaviour of both GNU dc (as specified in
its man page), and BSD dc (where stack_popstring() pops
only if the head is a string.)

Add a couple of tests to verify this behavior.

function                                             old     new   delta
zxc_vm_process                                      6882    6884      +2

Signed-off-by: Brian Foley <bpfoley@google.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 12 insertions, 1 deletions

diff --git a/miscutils/bc.c b/miscutils/bc.c
index 7ac30dd53..4a3ae49c5 100644
--- a/miscutils/bc.c
+++ b/miscutils/bc.c
@@ -6521,7 +6521,7 @@ static BC_STATUS zdc_program_execStr(char *code, size_t *bgn, bool cond)
                         if (s || !BC_PROG_STR(n)) goto exit;
                         sidx = n->rdx;
                 } else
-                        goto exit;
+                        goto exit_nopop;
         }
 
         fidx = sidx + BC_PROG_REQ_FUNCS;
@@ -6561,6 +6561,7 @@ static BC_STATUS zdc_program_execStr(char *code, size_t *bgn, bool cond)
         RETURN_STATUS(BC_STATUS_SUCCESS);
  exit:
         bc_vec_pop(&G.prog.results);
+ exit_nopop:
         RETURN_STATUS(s);
 }
 #define zdc_program_execStr(...) (zdc_program_execStr(__VA_ARGS__) COMMA_SUCCESS)
diff --git a/testsuite/dc.tests b/testsuite/dc.tests
index 8c3af4156..f74e3f0f5 100755
--- a/testsuite/dc.tests
+++ b/testsuite/dc.tests
@@ -44,6 +44,16 @@ testing "dc complex without spaces (multiple args)" \
 optional FEATURE_DC_BIG
 # All tests below depend on FEATURE_DC_BIG
 
+testing "dc: x should execute strings" \
+        "dc -e'[40 2 +] x f'" \
+        "42\n" \
+        "" ""
+
+testing "dc: x should not execute or pop non-strings" \
+        "dc -e'42 x f'" \
+        "42\n" \
+        "" ""
+
 testing "dc read" \
         "dc -finput" \
         "2\n9\n1\n" \