Last year a patch was submitted/approved/commited to eliminate symbol_matches_domain which was causing this problem. It was later reverted because it introduced a (severe) performance regression. Recap: (gdb) list 1 enum e {A,B,C} e; 2 int main (void) { return 0; } 3 (gdb) p e Attempt to use a type name as an expression The parser attempts to find a symbol named "e" of VAR_DOMAIN. This gets passed down through lookup_symbol and (eventually) into block_lookup_symbol_primary, which iterates over the block's dictionary of symbols: for (sym = dict_iter_name_first (block->dict, name, &dict_iter); sym != NULL; sym = dict_iter_name_next (name, &dict_iter)) { if (symbol_matches_domain (SYMBOL_LANGUAGE (sym), SYMBOL_DOMAIN (sym), domain)) return sym; } The problem here is that we have a symbol named "e" in both STRUCT_DOMAIN and VAR_DOMAIN, and for languages like C++, Java, and Ada, where a tag name may be used as an implicit typedef of the type, symbol_matches_domain ignores the difference between VAR_DOMAIN and STRUCT_DOMAIN. As it happens, the STRUCT_DOMAIN symbol is found first, considered a match, and that symbol is returned to the parser, eliciting the (now dreaded) error message. Since this bug exists specifically because we have both STRUCT and VAR_DOMAIN symbols in a given block/CU, this patch rather simply/naively changes block_lookup_symbol_primary so that it continues to search for an exact domain match on the symbol if symbol_matches_domain returns a symbol [RFC] Revisit PR 16253 ("Attempt to use a type name...") which does not exactly match the requested domain. This "fixes" the immediate problem, but admittedly might uncover other, related bugs. [Paranoia?] However, it causes no regressions (functional or performance) in the test suite. I have also resurrected the tests from the previous submission. However since we can still be given a matching symbol with a different domain than requested, we cannot say that a symbol "was not found." The error messages today will still be the (dreaded) "Attempt to use a type name..." I've updated the tests to reflect this. ChangeLog PR 16253 * block.c (block_lookup_symbol_primary): If a symbol is found which does not exactly match the requested domain, keep searching for an exact match. Otherwise, return the previously found "best" symbol. testsuite/ChangeLog PR 16253 * gdb.cp/var-tag.cc: New file. * gdb.cp/var-tag.exp: New file. --- gdb/ChangeLog | 8 ++++ gdb/block.c | 16 +++++-- gdb/testsuite/ChangeLog | 6 +++ gdb/testsuite/gdb.cp/var-tag.cc | 44 +++++++++++++++++++ gdb/testsuite/gdb.cp/var-tag.exp | 94 ++++++++++++++++++++++++++++++++++++++++ 5 files changed, 165 insertions(+), 3 deletions(-) create mode 100644 gdb/testsuite/gdb.cp/var-tag.cc create mode 100644 gdb/testsuite/gdb.cp/var-tag.exp ### a/gdb/ChangeLog ### b/gdb/ChangeLog ## -1,3 +1,11 @@ +2015-06-11 Keith Seitz + + PR 16253 + * block.c (block_lookup_symbol_primary): If a symbol is found + which does not exactly match the requested domain, keep searching + for an exact match. Otherwise, return the previously found "best" + symbol. + 2015-06-11 Gary Benson * nat/linux-namespaces.c (mnsh_send_message): Use pulongest. Index: gdb-7.9.1/gdb/block.c =================================================================== --- gdb-7.9.1.orig/gdb/block.c 2015-06-16 16:53:51.720719643 +0200 +++ gdb-7.9.1/gdb/block.c 2015-06-16 16:54:42.511031683 +0200 @@ -779,21 +779,31 @@ struct symbol * block_lookup_symbol_primary (const struct block *block, const char *name, const domain_enum domain) { - struct symbol *sym; + struct symbol *sym, *other; struct dict_iterator dict_iter; /* Verify BLOCK is STATIC_BLOCK or GLOBAL_BLOCK. */ gdb_assert (BLOCK_SUPERBLOCK (block) == NULL || BLOCK_SUPERBLOCK (BLOCK_SUPERBLOCK (block)) == NULL); + other = NULL; for (sym = dict_iter_name_first (block->dict, name, &dict_iter); sym != NULL; sym = dict_iter_name_next (name, &dict_iter)) { + if (SYMBOL_DOMAIN (sym) == domain) + return sym; + + /* This is a bit of a hack, but symbol_matches_domain might ignore + STRUCT vs VAR domain symbols. So if a matching symbol is found, make + sure there is no "better" matching symbol, i.e., one with + exactly the same domain. */ if (symbol_matches_domain (SYMBOL_LANGUAGE (sym), SYMBOL_DOMAIN (sym), domain)) - return sym; + { + other = sym; + } } - return NULL; + return other; } Index: gdb-7.9.1/gdb/testsuite/gdb.cp/var-tag.cc =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ gdb-7.9.1/gdb/testsuite/gdb.cp/var-tag.cc 2015-06-16 16:53:51.721719649 +0200 @@ -0,0 +1,44 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2014 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 . */ + +int global = 3; + +class C { +public: + struct C1 {} C1; + enum E1 {a1, b1, c1} E1; + union U1 {int a1; char b1;} U1; + + C () : E1 (b1) {} + void global (void) const {} + int f (void) const { global (); return 0; } +} C; + +struct S {} S; +enum E {a, b, c} E; +union U {int a; char b;} U; + +class CC {} cc; +struct SS {} ss; +enum EE {ea, eb, ec} ee; +union UU {int aa; char bb;} uu; + +int +main (void) +{ + return C.f (); +} Index: gdb-7.9.1/gdb/testsuite/gdb.cp/var-tag.exp =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ gdb-7.9.1/gdb/testsuite/gdb.cp/var-tag.exp 2015-06-16 16:53:51.721719649 +0200 @@ -0,0 +1,94 @@ +# Copyright 2014, 2015 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 + +# Test expressions in which variable names shadow tag names. + +if {[skip_cplus_tests]} { continue } + +standard_testfile .cc + +if {[prepare_for_testing $testfile.exp $testfile $srcfile {debug c++}]} { + return -1 +} + +proc do_global_tests {lang} { + set invalid_print "Attempt to use a type name as an expression" + set ptypefmt "type = (class|enum|union|struct) %s {.*}" + + with_test_prefix $lang { + gdb_test_no_output "set language $lang" + gdb_test "ptype C" "type = class C {.*}" + gdb_test "print E" "= a" + gdb_test "ptype E" "type = enum E {.*}" + gdb_test "print S" "= {}" + gdb_test "ptype S" "type = struct S {.*}" + gdb_test "print U" "= {.*}" + gdb_test "ptype U" "type = union U {.*}" + gdb_test "print cc" "= {.*}" + gdb_test "ptype cc" "type = class CC {.*}" + gdb_test "print CC" [format $invalid_print "CC"] + gdb_test "ptype CC" [format $ptypefmt "CC"] + gdb_test "print ss" "= {}" + gdb_test "ptype ss" "type = struct SS {.*}" + gdb_test "print SS" [format $invalid_print "SS"] + gdb_test "ptype SS" [format $ptypefmt "SS"] + gdb_test "print ee" "= .*" + gdb_test "ptype ee" "type = enum EE {.*}" + gdb_test "print EE" [format $invalid_print "EE"] + gdb_test "ptype EE" [format $ptypefmt "EE"] + gdb_test "print uu" "= {.*}" + gdb_test "ptype uu" "type = union UU {.*}" + gdb_test "print UU" [format $invalid_print "UU"] + gdb_test "ptype UU" [format $ptypefmt "UU"] + } +} + +# First test expressions when there is no context. +with_test_prefix "before start" { + do_global_tests c++ + do_global_tests c +} + +# Run to main and test again. +if {![runto_main]} { + perror "couldn't run to main" + continue +} + +with_test_prefix "in main" { + do_global_tests c++ + do_global_tests c +} + +# Finally run to C::f and test again +gdb_breakpoint "C::f" +gdb_continue_to_breakpoint "continue to C::f" +with_test_prefix "in C::f" { + do_global_tests c++ + do_global_tests c +} + +# Another hard-to-guess-the-users-intent bug... +# It would be really nice if we could query the user! +with_test_prefix "global collision" { + gdb_test_no_output "set language c++" + setup_kfail "c++/16463" "*-*-*" + gdb_test "print global" "= 3" + + # ... with a simple workaround: + gdb_test "print ::global" "= 3" +}