[Bug debug/54826] New: gdb test case failure (bs15503) due to gaps in lexical block

["arnez at linux dot vnet.ibm.com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54826

             Bug #: 54826
           Summary: gdb test case failure (bs15503) due to gaps in lexical
                    block
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: debug
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: arnez@linux.vnet.ibm.com


Current upstream gcc causes a regression with the gdb test case
bs15503.exp:
FAIL: gdb.cp/bs15503.exp: print s.length()
FAIL: gdb.cp/bs15503.exp: print s[0]
FAIL: gdb.cp/bs15503.exp: print s[s.length()-1]
FAIL: gdb.cp/bs15503.exp: print (const char *) s
FAIL: gdb.cp/bs15503.exp: print (const char *) s.substr(0,4)
FAIL: gdb.cp/bs15503.exp: print (const char *) (s=s.substr(0,4))

What happens is that the DWARF output for bs15503.cc wraps the string
variable "s" from StringTest<wchar_t>::testFunction() in a lexical
block with spurious gaps.  The test case happens to set a break point
into one of these gaps and tries to access the variable from there,
which gdb (correctly) refuses.

For reference, here's a link to the source code:
http://sourceware.org/cgi-bin/cvsweb.cgi/~checkout~/src/gdb/testsuite/gdb.cp/bs15503.cc?rev=1.11&cvsroot=src

I've verified the failure on x86_64 and s390x.  The regression was
introduced by: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=191494