[PATCH] Make gdb.python/python.exp more robust

[Luis Machado <lgustavo@codesourcery.com>]

I noticed gdb.python/python.exp failing on aarch64-elf like so:

FAIL: gdb.python/python.exp: Test decode_line func1 line number

This particular test expects the line number for func1 to be 19, hardcoded.

In my aarch64-elf tests gdb thinks func1 is at line 20, making the test fail.

The following patch addresses this by reading the line number information from
GDB and comparing it against the python decoded symtab information.

Regression tested on x86-64/Ubuntu 16.04.

gdb/testsuite/ChangeLog:

2017-01-20  Luis Machado  <lgustavo@codesourcery.com>

	* gdb.python/python.exp: Check line number against what GDB thinks
	the line number is for func1.
---
 gdb/testsuite/gdb.python/python.exp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/gdb.python/python.exp b/gdb/testsuite/gdb.python/python.exp
index 95ec74e..f099cc0 100644
--- a/gdb/testsuite/gdb.python/python.exp
+++ b/gdb/testsuite/gdb.python/python.exp
@@ -246,7 +246,17 @@ if { [is_remote host] } {
     set python_1_c [string_to_regexp "gdb.python/python-1.c"]
 }
 gdb_test "python print (symtab\[1\]\[0\].symtab)" ".*${python_1_c}" "test decode_line func1 filename"
-gdb_test "python print (symtab\[1\]\[0\].line)" "19" "test decode_line func1 line number"
+
+# Fetch the line GDB thinks func1 starts at.  This may change depending
+# on the architecture and on how GDB handles the prologue of the function.
+gdb_test_multiple "info line func1" "info line func1" {
+    -re "Line ($decimal) of .* starts at address $hex <func1> and ends at $hex <func1\\+$decimal>\.\[\r\n\]+$gdb_prompt $" {
+	# Fetch the line number.
+	set func1_lineno $expect_out(1,string)
+    }
+}
+
+gdb_test "python print (symtab\[1\]\[0\].line)" "$func1_lineno" "test decode_line func1 line number"
 gdb_py_test_silent_cmd {python symtab = gdb.decode_line ("func1,func2")} \
     "test decode_line func1,func2" 1
 gdb_test {python print (symtab[0])} ",func2" "stop at comma in linespec"
-- 
2.7.4