[PATCH v3 01/14] gdb/testsuite: introduce gdb_step_until_regexp

[Bruno Larsen <blarsen@redhat.com>]

Currently, GDB's testsuite uses a set amount of step commands to exit
functions. This is a problem if a compiler emits different epilogue
information from gcc, or emits no epilogue information at all. It was
most noticeable if Clang was used to test GDB.

To fix this unreliability, this commit introduces a new proc that will
single step the inferior until it is stopped at a line that matches the
given regexp, or until it steps too many times - defined as an optional
argument. If the line is found, it shows up as a single PASS in the
test, and if the line is not found, a single FAIL is emitted.

This patch only introduces this proc, but does not add it to any
existing tests, these will be introduced in the following commit.
---

No change in v3

New patch in v2

---
 gdb/testsuite/lib/gdb.exp | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index b04fbb89e4e..c0ca1d04cc2 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -8648,5 +8648,35 @@ proc get_set_option_choices {set_cmd} {
     return $values
 }
 
+# This proc is used mainly to exit function in a compiler agnostic way
+# It makes gdb single step and evaluate the output at every step, to see
+# if the regexp is present.
+#
+# The proc takes 2 optional arguments, the first being the name of the
+# test and the second the maximum amount of iterations until we expect to
+# see the function. The default is 10 steps, since this is meant as the
+# last step by default, and we don't expect any compiler generated epilogue
+# longer than 10 steps.
+
+proc gdb_step_until_regexp { regexp {test_name "single stepping until regexp"} {max_steps 10} } {
+    global gdb_prompt
+
+    set count 0
+    gdb_test_multiple "step" "$test_name" {
+	-re "$regexp\r\n$gdb_prompt $" {
+	    pass $test_name
+	}
+	-re ".*$gdb_prompt $" {
+	    if {$count < $max_steps} {
+		incr count
+		send_gdb "step\n"
+		exp_continue
+	    } else {
+		fail $test_name
+	    }
+	}
+    }
+}
+
 # Always load compatibility stuff.
 load_lib future.exp
-- 
2.31.1