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# Copyright 2002, 2004, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 3 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program.  If not, see .

# This file is part of the gdb testsuite

# Looking up methods by name, in programs with multiple compilation units.

# ====== PLEASE BE VERY CAREFUL WHEN CHANGING THIS TEST. =====

#

# The bug we're testing for (circa October 2002) is very sensitive to

# various conditions that are hard to control directly in the test

# suite.  If you change the test, please revert this change, and make

# sure the test still fails:

#

# 2002-08-29  Jim Blandy  

#

#       * symtab.c (lookup_symbol_aux): In the cases where we find a

#       minimal symbol of an appropriate name and use its address to

#       select a symtab to read and search, use `name' (as passed to us)

#       as the demangled name when searching the symtab's global and

#       static blocks, not the minsym's name.

#

# The original bug was that you'd try to set a breakpoint on a method

# (e.g., `break s::method1'), and you'd get an error, but if you

# repeated the command, it would work the second time:

#

#   (gdb) break s::method1

#   the class s does not have any method named method1

#   Hint: try 's::method1 or 's::method1

#   (Note leading single quote.)

#   (gdb) break s::method1

#   Breakpoint 1 at 0x804841b: file psmang1.cc, line 13.

#   (gdb)

#

# We observed this bug first using Stabs, and then using Dwarf 2.

#

# The problem was in lookup_symbol_aux: when looking up s::method1, it

# would fail to find it in any symtabs, find the minsym with the

# corresponding mangled name (say, `_ZN1S7method1Ev'), pass the

# minsym's address to find_pc_sect_symtab to look up the symtab

# (causing the compilation unit's full symbols to be read in), and

# then look up the symbol in that symtab's global block.  All that is

# correct.  However, it would pass the minsym's name as the NAME

# argument to lookup_block_symbol; a minsym's name is mangled, whereas

# lookup_block_symbol's NAME argument should be demangled.

#

# This is a pretty simple bug, but it turns out to be a bear to

# construct a test for.  That's why this test case is so delicate.  If

# you can see how to make it less so, please contribute a patch.

#

# Here are the twists:

#

# The bug only manifests itself when we call lookup_symbol to look up

# a method name (like "s::method1" or "s::method2"), and that method's

# definition is in a compilation unit for which we have read partial

# symbols, but not full symbols.  The partial->full conversion must be

# caused by that specific lookup.  (If we already have full symbols

# for the method's compilation unit, we won't need to look up the

# minsym, find the symtab for the minsym's address, and then call

# lookup_block_symbol; it's that last call where things go awry.)

#

# Now, when asked to set a breakpoint at `s::method1', GDB will first

# look up `s' to see if that is, in fact, the name of a class, and

# then look up 's::method1'.  So we have to make sure that looking up

# `s' doesn't cause full symbols to be read for the compilation unit

# containing the definition of `s::method1'.

#

# The partial symbol tables for `psmang1.cc' and `psmang2.cc' will

# both have entries for `s'; GDB will read full symbols for whichever

# compilation unit's partial symbol table appears first in the

# objfile's list.  The order in which compilation units appear in the

# partial symbol table list depends on how the program is linked, and

# how the debug info reader does the partial symbol scan.  Ideally,

# the test shouldn't rely on them appearing in any particular order.

#

# So, since we don't know which compilation unit's full symbols are

# going to get read, we simply try looking up one method from each of

# the two compilation units.  One of them has to come after the other

# in the partial symbol table list, so whichever comes later will

# still need its partial symbols read by the time we go to look up

# 's::methodX'.

#

# Second twist: don't move the common definition of `struct s' into a

# header file.  If the compiler emits identical stabs for the

# #inclusion of that header file into psmang1.cc and into psmang2.cc,

# then the linker will do stabs compression, and replace one of the

# BINCL/EINCL regions with an EXCL stab, pointing to the other

# BINCL/EINCL region.  GDB will read this, and record that the

# compilation unit that got the EXCL depends on the compilation unit

# that kept the BINCL/EINCL.  Then, when it decides it needs to read

# full symbols for the former, it'll also read full symbols for the

# latter.  Now, if it just so happens that the compilation unit that

# got the EXCL is also the first one with a definition of `s' in the

# partial symbol table list, then that first probe for `s' will cause

# both compilation units' full symbols to be read --- again defeating

# the test.

#

# We could work around this by having three compilation units, or by

# ensuring that the header file produces different stabs each time

# it's #included, but it seems simplest just to avoid compilation unit

# dependencies altogether, drop the header file, and duplicate the

# (pretty trivial) struct definition.

#

# Note that #including any header file at all into both compilation

# units --- say,  --- could create this sort of dependency.

#

# This is the aspect of the test which the debug format is most likely

# to affect, I think.  The different formats create different kinds of

# inter-CU dependencies, which could mask the bug.  It might be

# possible for the test to check that at least one of the partial

# symtabs remains unread, and fail otherwise --- the failure

# indicating that the test itself isn't going to catch the bug it was

# meant to, not that GDB is misbehaving.

#

# Third twist: given the way lookup_block_symbol is written, it's

# possible to find the symbol even when it gets passed a mangled name

# for its NAME parameter.  There are three ways lookup_block_symbol

# might search a block, depending on how it was constructed:

#

# linear search.  In this case, this bug will never manifest itself,

# since we check every symbol against NAME using SYMBOL_MATCHES_NAME.

# Since that macro checks its second argument (NAME) against both the

# mangled and demangled names of the symbol, this will always find the

# symbol successfully, so, no bug.

#

# hash table.  If both the mangled and demangled names hash to the

# same bucket, then you'll again find the symbol "by accident", since

# we search the entire bucket using SYMBOL_SOURCE_NAME.  Since GDB

# chooses the number of buckets based on the number of symbols, small

# compilation units may have only one hash bucket; in this case, the

# search always succeeds, even though we hashed on the wrong name.

# This test works around that by having a lot of dummy variables,

# making it less likely that the mangled and demangled names fall in

# the same bucket.

#

# binary search.  (GDB 5.2 produced these sorts of blocks, and this

# test tries to detect the bug there, but subsequent versions of GDB

# almost never build them, and they may soon be removed entirely.)  In

# this case, the symbols in the block are sorted by their

# SYMBOL_SOURCE_NAME (whose behavior depends on the current demangling

# setting, so that's wrong, but let's try to stay focussed).

# lookup_block_symbol does a binary search comparing NAME with

# SYMBOL_SOURCE_NAME until the range has been narrowed down to only a

# few symbols; then it starts a linear search forward from the lower

# end of that range, until it reaches a symbol whose

# SYMBOL_SOURCE_NAME follows NAME in lexicographic order.  This means

# that, if you're doing a binary search for a mangled name in a block

# sorted by SYMBOL_SOURCE_NAME, you might find the symbol `by

# accident' if the mangled and demangled names happen to fall near

# each other in the ordering.  The initial version of this patch used

# a class called `S'; all the other symbols in the compilation unit

# started with lower-case letters, so the demangled name `S::method1'

# sorted at the same place as the mangled name `_ZN1S7method1Ev': at

# the very beginning.  Using a lower-case 's' as the name ensures that

# the demangled name falls after all the dummy symbols introduced for

# the hash table, as described above.

#

# This is all so tortured, someone will probably come up with still

# other ways this test could fail to do its job.  If you need to make

# revisions, please be very careful.

if $tracelevel then {

    strace $tracelevel

}

#

# test running programs

#

if { [skip_cplus_tests] } { continue }

set testfile "psmang"

set binfile ${objdir}/${subdir}/${testfile}

if [get_compiler_info ${binfile} "c++"] {

    return -1;

}

if  { [gdb_compile "${srcdir}/${subdir}/${testfile}1.cc" "${testfile}1.o" object {debug c++}] != "" } {

     untested psmang.exp

     return -1

}

if  { [gdb_compile "${srcdir}/${subdir}/${testfile}2.cc" "${testfile}2.o" object {debug c++}] != "" } {

     untested psmang.exp

     return -1

}

if  { [gdb_compile "${testfile}1.o ${testfile}2.o" ${binfile} executable {debug c++}] != "" } {

     untested psmang.exp

     return -1

}

gdb_exit

gdb_start

gdb_reinitialize_dir $srcdir/$subdir

gdb_load ${binfile}

gdb_test "break s::method1" "Breakpoint .* at .*: file .*psmang1.cc.*"

# We have to exit and restart GDB here, to make sure that all the

# compilation units are psymtabs again.

gdb_exit

gdb_start

gdb_reinitialize_dir $srcdir/$subdir

gdb_load ${binfile}

gdb_test "break s::method2" "Breakpoint .* at .*: file .*psmang2.cc.*"