Re: Avoid timeouts in call-sc.exp

[Michael Chastain <mec.gnu@mindspring.com>]

Paul Gilliam <pgilliam@us.ibm.com> wrote:
> The test "call-sc.exp" will attemt to "finish" from main if the prevous 
> "return foo" failed.  Here is what happens:
>
> 257		gdb_test_multiple "return foo" "${test}" {
>
> If this works, then we are in "main".  If it doesn't work (say, due to a gdb 
> bug) then we are left in the function "fun".

First, can you post the gdb.log section for call-sc.exp on your
platform that is failing.  Also, what system is it and what
compiler are you using to run the test suite?

Good analysis, but I think your fix is too complicated and stateful.
I'd like a different approach to this.  Rather than handling various
different places where the program counter could be, it would be
better to do this at the end of the "return foo" test.
Something like this:

  # If the previous test did not work, the program counter might
  # still be inside foo() rather than main().  Get the program
  # counter back to main().
  #
  # This happens on [system] with [compiler].

  set try_finish 0
  set test "return foo; synchronize pc to main"
  gdb_test_multiple "backtrace 1" $test {
    -re "#0.*main \\(\\).*$gdb_prompt $" {
      pass $test
    }
    -re "#0.*fun \\(\\).*$gdb_prompt $" {
      if { $try_finish == 0 } {
	incr try_finish
	gdb_test "finish" ".*" ""
	exp_continue
      }
      fail $test
    }
  }

Also there is a pre-existing cut-and-paste error in the body of
"Make fun return now":

	-re "Make fun return now.*y or n. $" {
	    gdb_test_multiple "y" "${test}" {
		-re "L *= fun.*${gdb_prompt} $" {
		    # Need to step off the function call
		    gdb_test "next" "zed.*" "${test}"
		}
		-re "L[expr  + 1] *= fun[expr  + 1].*${gdb_prompt} $" {
		    pass "${test}"
		}
	    }
	}

The second arm, "L[expr  + 1] *= ...", is supposed to handle the case
where returning from "fun" lands on the line after the call to "fun".
This happens when the compiler generates code so that the last assembly
instruction in "L = fun ();" is the actual assembly-language call
instruction.  But the regular expression is wrong, it was copied from
structs.exp and it was meant for structs.c and does not work with
call-sc.c.

I'll make a patch for the cut-and-pasto first.  If you want to turn
the code snippet with "try_finish" into a patch and do some testing,
that would be great.  Or I could make that into a patch.

Michael