[Bug c++/11606] New: multiple inferior calls with struct return values behave not well.

[Bug c++/11606] New: multiple inferior calls with struct return values behave not well.

[andre dot poenitz at nokia dot com]

Evaluating expressions involving sequences of calls with non-trivial
intermediate values produce errors like "Attempt to take address of value not
located in memory." or, in other cases, gdb reporting SIGSEGV in the inferior.

To reproduce:

  echo 'struct S {}; S f() { return S(); } S g(const S &s) { return s; } int
main() { S s = g(f()); }' | g++ -xc++ -o x -g -
  gdb -ex 'b main' -ex run -ex 'p g(f())' ./x

My guess is that the result of the call is transfered from the inferior into
gdb, but not "moved back" for further processing.

The problem can be partially worked around by manually disentangling the calls
and "poking" the intermediate results back into the inferior using something like

def makeValue(type, init):
    gdb.execute("set $d = (%s*)malloc(sizeof(%s))" % (type, type))
    gdb.execute("set *$d = {%s}" % init)
    return gdb.parse_and_eval("$d").dereference()

-- 
           Summary: multiple inferior calls with struct return values behave
                    not well.
           Product: gdb
           Version: 7.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at sourceware dot org
        ReportedBy: andre dot poenitz at nokia dot com
                CC: gdb-prs at sourceware dot org
 GCC build triplet: i486-linux-gnu, applies to any
  GCC host triplet: i486-linux-gnu, applies to any
GCC target triplet: i486-linux-gnu, applies to any


http://sourceware.org/bugzilla/show_bug.cgi?id=11606

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[Bug c++/11606] multiple inferior calls with struct return values behave not well.

[pedro at codesourcery dot com]

------- Additional Comments From pedro at codesourcery dot com  2010-05-17 11:06 -------
Are you saying that the same example sometimes crashes the inferior, while
sometimes results in the "Attempt to take address of value not located in
memory." error, or do you need a different reproducer to cause
SIGSEGV crash in the inferior?  If the latter, do you have such a
reproducer?


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[Bug c++/11606] multiple inferior calls with struct return values behave not well.

[andre dot poenitz at nokia dot com]

------- Additional Comments From andre dot poenitz at nokia dot com  2010-05-17 13:32 -------
The example given always produces "Attempt to take address of value not
located in memory." as far as I can tell.

The SIGSEGV reports have been showing up in a somewhat more complex setup
involving Qt Creator's pretty-printers for QObject and QModelIndex that also
uses cascaded inferior calls.

I believe the problem is the same, though and would like to save me the trouble
to cut this down to something that's reproducible without a lot of external
dependencies.

Sorry for the confusion.

-- 


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[Bug c++/11606] multiple inferior calls with struct return values behave not well.

[swagiaal at redhat dot com]

------- Additional Comments From swagiaal at redhat dot com  2010-08-05 15:12 -------
Created an attachment (id=4913)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4913&action=view)
test case


-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=11606

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[Bug c++/11606] GDB does not properly implement the default copy constructor

[swagiaal at redhat dot com]

------- Additional Comments From swagiaal at redhat dot com  2010-08-05 15:13 -------
While the example mentioned can be fixed by setting the lval of the value
returned by call_function_by_hand() lval_memory further nesting does not work.
example attached.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
            Summary|multiple inferior calls with|GDB does not properly
                   |struct return values behave |implement the default copy
                   |not well.                   |constructor


http://sourceware.org/bugzilla/show_bug.cgi?id=11606

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[Bug c++/11606] GDB does not properly implement the default copy constructor

[swagiaal at redhat dot com]

------- Additional Comments From swagiaal at redhat dot com  2010-08-06 21:34 -------
This issue was also discussed here:
http://www.cygwin.com/ml/gdb-patches/2010-08/msg00053.html

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |swagiaal at redhat dot com


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