From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Snyder To: Eli Zaretskii Cc: zackw@stanford.edu, gdb-patches@sources.redhat.com Subject: Re: Option to elide single-bit bitfields when printing structures Date: Fri, 23 Feb 2001 10:09:00 -0000 Message-id: <3A96A65C.6264@redhat.com> References: <20010222115633.B11707@wolery.stanford.edu> <200102230756.CAA06304@indy.delorie.com> X-SW-Source: 2001-02/msg00451.html Eli Zaretskii wrote: > > > From: "Zack Weinberg" > > Date: Thu, 22 Feb 2001 11:56:33 -0800 > > > > (gdb) p decl->common > > $1 = {chain = 0x40253000, type = 0x40253138, code = FUNCTION_DECL, > > side_effects_flag = 0, constant_flag = 0, addressable_flag = 0, > > volatile_flag = 0, readonly_flag = 0, unsigned_flag = 0, > > asm_written_flag = 0, used_flag = 0, nothrow_flag = 0, static_flag = 0, > > public_flag = 1, private_flag = 0, protected_flag = 0, bounded_flag = 0, > > lang_flag_0 = 0, lang_flag_1 = 0, lang_flag_2 = 0, lang_flag_3 = 0, > > lang_flag_4 = 0, lang_flag_5 = 0, lang_flag_6 = 0, dummy = 0} > > > > It's hard to see which are set and which aren't. With this patch, you > > can get it printed like this: > > > > (gdb) set print elide-bitflags on > > (gdb) p decl->common > > $2 = {chain = 0x40253000, type = 0x40253138, code = FUNCTION_DECL, public_flag} > > > > which is, IMHO, much easier to read. > > What if someone wants to know which flags are _reset_? What if there > are more than one set flag in your example? What if the bit fields > span more than one bit? I don't see how your suggestion would deal > with these cases in a way that the resulting display is > self-explaining. That trailing "public_flag" is already hard to > understand; I stared at it for a few moments without understanding > what's going on here, before it hit me. > > Perhaps we need a special command or a special format that would put > the burden on the user. For example, if the user specifies exactly > what flags (set or unset) does she want to see, the display doesn't > need to explain that, because the user asked for it. > > > * cp-valprint.c (elide_bitflag_print): New flag. > > (cp_print_value_fields): If elide_bitflag_print, skip printing > > single-bit fields whose value is zero entirely, and skip > > printing the value for single-bit fields whose value is one. > > (_initialize_cp_valprint): Add 'set print elide-bitflags' > > command, default to old behavior. > > If these changes are approved by the cp-valprint maintainer, please > add some minimal changes in gdb.texinfo which describe this feature. I don't think this feature is necessary. This is just an instance of special display of data. This is what the gdb scripting language is for.