[PATCH 5/6] gdb/testsuite: fix gdb.debuginfod/fetch_src_and_symbols.exp with Clang

[Andrew Burgess <aburgess@redhat.com>]

The gdb.debuginfod/fetch_src_and_symbols.exp test is showing a single
failure when run with some older versions of Clang, e.g. 9.0.1.

The problem appears to be with Clang's generated line table.  The test
source looks like this:

  int
  main()
  {
    asm ("main_label: .globl main_label");
    return 0;
  }

In GDB, when we 'start', we expect to stop at the 'return 0;' line.
This is the behaviour when the compiler is gcc, or later versions of
Clang.

However, with Clang 9.0.2, I see GDB stop on the 'asm' line.

I propose adding some code to the test script to step GDB onto the
next line if we stop on the 'asm' line.  With this change in place, I
now see the test fully passing with Clang 9.0.1 and 15.0.2, as well as
with gcc.
---
 .../gdb.debuginfod/fetch_src_and_symbols.exp  | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/gdb/testsuite/gdb.debuginfod/fetch_src_and_symbols.exp b/gdb/testsuite/gdb.debuginfod/fetch_src_and_symbols.exp
index b57b3201cf7..cebaa435102 100644
--- a/gdb/testsuite/gdb.debuginfod/fetch_src_and_symbols.exp
+++ b/gdb/testsuite/gdb.debuginfod/fetch_src_and_symbols.exp
@@ -161,6 +161,27 @@ proc_with_prefix no_url { } {
     if ![runto_main] {
 	return -1
     }
+
+    # Some older versions of Clang (e.g. 9.0.1) were observed stopped
+    # at the 'asm' line rather than the 'return' line in main.c.  This
+    # messes up some of the expected patterns later in the test.
+    set rtn_lineno [gdb_get_line_number "return 0;"]
+    set prev_lineno [expr $rtn_lineno - 1]
+    gdb_test_multiple "info line" "" {
+	-wrap -re "\r\nLine ${prev_lineno} of .*" {
+	    gdb_test "step"
+	    pass $gdb_test_name
+	}
+	-wrap -re "\r\nLine ${rtn_lineno} of .*" {
+	    pass $gdb_test_name
+	}
+	-wrap -re "\r\nLine ${::decimal} of .*" {
+	    # Not sure what line this stopped on, but later tests are
+	    # probably going to fail.
+	    fail $gdb_test_name
+	}
+    }
+
     gdb_test "generate-core-file $::corefile" "Saved corefile $::corefile" \
 	"file [file tail $::corefile] gen"
     file rename -force ${binfile}2 $debugdir
-- 
2.25.4