From bde240e7f83f208568254574082df12c871dcbc8 Mon Sep 17 00:00:00 2001 From: Andrew Burgess Date: Wed, 31 May 2023 16:14:47 +0100 Subject: [PATCH] gdb: fix printf of wchar_t early in a gdb session Given this test program: #include const wchar_t wide_str[] = L"wide string"; int main (void) { return 0; } I observed this GDB behaviour: $ gdb -q /tmp/printf-wchar_t Reading symbols from /tmp/printf-wchar_t... (gdb) start Temporary breakpoint 1 at 0x40110a: file /tmp/printf-wchar_t.c, line 8. Starting program: /tmp/printf-wchar_t Temporary breakpoint 1, main () at /tmp/printf-wchar_t.c:8 25 return 0; (gdb) printf "%ls\n", wide_str (gdb) Notice that the printf results in a blank line rather than the expected 'wide string' output. I tracked the problem down to printf_wide_c_string (in printcmd.c), in this function we do this: struct type *wctype = lookup_typename (current_language, "wchar_t", NULL, 0); int wcwidth = wctype->length (); the problem here is that 'wchar_t' is a typedef. If we look at the comment on type::length() we see this: /* Note that if thistype is a TYPEDEF type, you have to call check_typedef. But check_typedef does set the TYPE_LENGTH of the TYPEDEF type, so you only have to call check_typedef once. Since value::allocate calls check_typedef, X->type ()->length () is safe. */ What this means is that after calling lookup_typename we should call check_typedef in order to ensure that the length of the typedef has been setup correctly. We are not doing this in printf_wide_c_string, and so wcwidth is incorrectly calculated as 0. This is what leads GDB to print an empty string. We can see in c_string_operation::evaluate (in c-lang.c) an example of calling check_typedef specifically to fix this exact issue. Initially I did fix this problem by adding a check_typedef call into printf_wide_c_string, but then I figured why not move the check_typedef call up into lookup_typename itself, that feels like it should be harmless when looking up a non-typedef type, but will avoid bugs like this when looking up a typedef. So that's what I did. I can then remove the extra check_typedef call from c-lang.c, I don't see any other places where we had extra check_typedef calls. This doesn't mean we definitely had bugs -- so long as we never checked the length, or, if we knew that check_typedef had already been called, then we would be fine. I don't see any test regressions after this change, and my new test case is now passing. Reviewed-By: Tom Tromey --- gdb/c-lang.c | 3 --- gdb/gdbtypes.c | 11 ++++++---- gdb/gdbtypes.h | 14 ++++++++++-- gdb/testsuite/gdb.base/printf-wchar_t.c | 26 +++++++++++++++++++++++ gdb/testsuite/gdb.base/printf-wchar_t.exp | 26 +++++++++++++++++++++++ 5 files changed, 71 insertions(+), 9 deletions(-) create mode 100644 gdb/testsuite/gdb.base/printf-wchar_t.c create mode 100644 gdb/testsuite/gdb.base/printf-wchar_t.exp diff --git a/gdb/c-lang.c b/gdb/c-lang.c index b71457bd25f..99cbbff94fa 100644 --- a/gdb/c-lang.c +++ b/gdb/c-lang.c @@ -615,9 +615,6 @@ c_string_operation::evaluate (struct type *expect_type, internal_error (_("unhandled c_string_type")); } - /* Ensure TYPE_LENGTH is valid for TYPE. */ - check_typedef (type); - /* If the caller expects an array of some integral type, satisfy them. If something odder is expected, rely on the caller to cast. */ diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c index 9aa644b7990..c5272979cb9 100644 --- a/gdb/gdbtypes.c +++ b/gdb/gdbtypes.c @@ -1648,9 +1648,7 @@ type_name_or_error (struct type *type) objfile ? objfile_name (objfile) : ""); } -/* Lookup a typedef or primitive type named NAME, visible in lexical - block BLOCK. If NOERR is nonzero, return zero if NAME is not - suitably defined. */ +/* See gdbtypes.h. */ struct type * lookup_typename (const struct language_defn *language, @@ -1662,7 +1660,12 @@ lookup_typename (const struct language_defn *language, sym = lookup_symbol_in_language (name, block, VAR_DOMAIN, language->la_language, NULL).symbol; if (sym != NULL && sym->aclass () == LOC_TYPEDEF) - return sym->type (); + { + struct type *type = sym->type (); + /* Ensure the length of TYPE is valid. */ + check_typedef (type); + return type; + } if (noerr) return NULL; diff --git a/gdb/gdbtypes.h b/gdb/gdbtypes.h index 8071d6b97ae..aedaf53cd5d 100644 --- a/gdb/gdbtypes.h +++ b/gdb/gdbtypes.h @@ -2586,8 +2586,18 @@ extern void check_stub_method_group (struct type *, int); extern char *gdb_mangle_name (struct type *, int, int); -extern struct type *lookup_typename (const struct language_defn *, - const char *, const struct block *, int); +/* Lookup a typedef or primitive type named NAME, visible in lexical block + BLOCK. If NOERR is nonzero, return zero if NAME is not suitably + defined. + + If this function finds a suitable type then check_typedef is called on + the type, this ensures that if the type being returned is a typedef + then the length of the type will be correct. The original typedef will + still be returned, not the result of calling check_typedef. */ + +extern struct type *lookup_typename (const struct language_defn *language, + const char *name, + const struct block *block, int noerr); extern struct type *lookup_template_type (const char *, struct type *, const struct block *); diff --git a/gdb/testsuite/gdb.base/printf-wchar_t.c b/gdb/testsuite/gdb.base/printf-wchar_t.c new file mode 100644 index 00000000000..4d13fd3c961 --- /dev/null +++ b/gdb/testsuite/gdb.base/printf-wchar_t.c @@ -0,0 +1,26 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2023 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 . */ + +#include + +const wchar_t wide_str[] = L"wide string"; + +int +main (void) +{ + return 0; +} diff --git a/gdb/testsuite/gdb.base/printf-wchar_t.exp b/gdb/testsuite/gdb.base/printf-wchar_t.exp new file mode 100644 index 00000000000..85c6edf292c --- /dev/null +++ b/gdb/testsuite/gdb.base/printf-wchar_t.exp @@ -0,0 +1,26 @@ +# Copyright 2023 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 . + +standard_testfile + +if {[prepare_for_testing "failed to prepare" $testfile $srcfile]} { + return -1 +} + +if {![runto_main]} { + return -1 +} + +gdb_test {printf "%ls\n", wide_str} "^wide string"