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From: sergiodj+buildbot@sergiodj.net To: gdb-testers@sourceware.org Subject: [binutils-gdb] Introduce obstack_new, poison other "typed" obstack functions Date: Mon, 21 May 2018 01:51:00 -0000 [thread overview] Message-ID: <284a0e3cbffa92ee5c94065fcdd5a528482344fc@gdb-build> (raw) *** TEST RESULTS FOR COMMIT 284a0e3cbffa92ee5c94065fcdd5a528482344fc *** Author: Simon Marchi <simon.marchi@ericsson.com> Branch: master Commit: 284a0e3cbffa92ee5c94065fcdd5a528482344fc Introduce obstack_new, poison other "typed" obstack functions Since we use obstacks with objects that are not default constructible, we sometimes need to manually call the constructor by hand using placement new: foo *f = obstack_alloc (obstack, sizeof (foo)); f = new (f) foo; It's possible to use allocate_on_obstack instead, but there are types that we sometimes want to allocate on an obstack, and sometimes on the regular heap. This patch introduces a utility to make this pattern simpler if allocate_on_obstack is not an option: foo *f = obstack_new<foo> (obstack); Right now there's only one usage (in tdesc_data_init). To help catch places where we would forget to call new when allocating such an object on an obstack, this patch also poisons some other methods of allocating an instance of a type on an obstack: - OBSTACK_ZALLOC/OBSTACK_CALLOC - XOBNEW/XOBNEW - GDBARCH_OBSTACK_ZALLOC/GDBARCH_OBSTACK_CALLOC Unfortunately, there's no way to catch wrong usages of obstack_alloc. By pulling on that string though, it tripped on allocating struct template_symbol using OBSTACK_ZALLOC. The criterion currently used to know whether it's safe to "malloc" an instance of a struct is whether it is a POD. Because it inherits from struct symbol, template_symbol is not a POD. This criterion is a bit too strict however, it should still safe to allocate memory for a template_symbol and memset it to 0. We didn't use is_trivially_constructible as the criterion in the first place only because it is not available in gcc < 5. So here I considered two alternatives: 1. Relax that criterion to use std::is_trivially_constructible and add a bit more glue code to make it work with gcc < 5 2. Continue pulling on the string and change how the symbol structures are allocated and initialized I managed to do both, but I decided to go with #1 to keep this patch simpler and more focused. When building with a compiler that does not have is_trivially_constructible, the check will just not be enforced. gdb/ChangeLog: * common/traits.h (HAVE_IS_TRIVIALLY_COPYABLE): Define if compiler supports std::is_trivially_constructible. * common/poison.h: Include obstack.h. (IsMallocable): Define to is_trivially_constructible if the compiler supports it, define to true_type otherwise. (xobnew): New. (XOBNEW): Redefine. (xobnewvec): New. (XOBNEWVEC): Redefine. * gdb_obstack.h (obstack_zalloc): New. (OBSTACK_ZALLOC): Redefine. (obstack_calloc): New. (OBSTACK_CALLOC): Redefine. (obstack_new): New. * gdbarch.sh: Include gdb_obstack in gdbarch.h. (gdbarch_obstack): New declaration in gdbarch.h, definition in gdbarch.c. (GDBARCH_OBSTACK_CALLOC, GDBARCH_OBSTACK_ZALLOC): Use obstack_calloc/obstack_zalloc. (gdbarch_obstack_zalloc): Remove. * target-descriptions.c (tdesc_data_init): Use obstack_new.
next reply other threads:[~2018-05-21 1:47 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-05-21 1:51 sergiodj+buildbot [this message] 2018-05-21 1:51 ` Failures on Debian-s390x-m64, branch master sergiodj+buildbot 2018-05-21 1:52 ` Failures on Fedora-s390x-m64, " sergiodj+buildbot 2018-05-28 15:37 ` Failures on Fedora-x86_64-m64, " sergiodj+buildbot 2018-05-28 15:58 ` Failures on Fedora-i686, " sergiodj+buildbot 2018-05-28 18:12 ` Failures on Fedora-x86_64-cc-with-index, " sergiodj+buildbot 2018-05-28 18:25 ` *** COMPILATION FAILED *** Failures on Fedora-x86_64-w64-mingw32, branch master *** BREAKAGE *** sergiodj+buildbot 2018-07-27 1:33 ` Failures on Ubuntu-AArch32-m32, branch master sergiodj+buildbot 2018-07-27 5:00 ` Failures on Ubuntu-AArch32-native-extended-gdbserver-m32, " sergiodj+buildbot
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