From 7d72802bfc3fc52fe0f35854694941c9534e0bcb Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Fri, 23 Oct 2020 18:49:48 +0200 Subject: [PATCH] [gdb/testsuite] Don't use default form in Dwarf::_guess_form The only possible form for a DW_AT_low_pc attribute is DW_FORM_addr. When specifying in dwarf assembly a low_pc attribute without explicit form: ... {low_pc {main_label - 4}} ... the resulting attribute uses DW_FORM_string, which is misinterpreted by gdb when reading it as: ... cu->base_address = attr->as_address (); ... Stop using DW_FORM_string as default form. Instead, use a default form based on the attribute name, if possible and unambiguous. Otherwise, error out. F.i.: - for DW_AT_low_pc we use DW_FORM_addr. - For DW_AT_high_pc, we don't specify a default form because it could be either address or constant class. - For DW_AT_name, we use DW_FORM_string. While we could encode with DW_FORM_strp instead, DW_FORM_string is always ok. Tested on x86_64-linux. gdb/testsuite/ChangeLog: 2020-10-23 Tom de Vries * lib/dwarf.exp (Dwarf::_guess_form): Return "" by default instead of DW_FORM_string. (Dwarf::_default_form): New proc. (Dwarf::_handle_DW_TAG): Use _default_form. Error out if no form was guessed. --- gdb/testsuite/ChangeLog | 8 ++++++++ gdb/testsuite/lib/dwarf.exp | 35 ++++++++++++++++++++++++++--------- 2 files changed, 34 insertions(+), 9 deletions(-) diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 2683237a34f..e2944f21806 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,11 @@ +2020-10-23 Tom de Vries + + * lib/dwarf.exp (Dwarf::_guess_form): Return "" by default instead of + DW_FORM_string. + (Dwarf::_default_form): New proc. + (Dwarf::_handle_DW_TAG): Use _default_form. Error out if no form was + guessed. + 2020-10-23 Tom de Vries * gdb.dwarf2/ada-linkage-name.exp: Use $srcfile for DW_AT_name of CU. diff --git a/gdb/testsuite/lib/dwarf.exp b/gdb/testsuite/lib/dwarf.exp index 5c840631052..1a0cbf689e6 100644 --- a/gdb/testsuite/lib/dwarf.exp +++ b/gdb/testsuite/lib/dwarf.exp @@ -247,11 +247,10 @@ proc get_func_info { name {options {debug}} } { # and DW_FORM_ref4 is used. See 'new_label' and 'define_label'. # * If VALUE starts with the "%" character, then it is a label # reference too, but DW_FORM_ref_addr is used. -# * Otherwise, VALUE is taken to be a string and DW_FORM_string is -# used. In order to prevent bugs where a numeric value is given but -# no form is specified, it is an error if the value looks like a number -# (using Tcl's "string is integer") and no form is provided. -# More form-guessing functionality may be added. +# * Otherwise, if the attribute name has a default form (f.i. DW_FORM_addr for +# DW_AT_low_pc), then that one is used. +# * Otherwise, an error is reported. Either specify a form explicitly, or +# add a default for the the attribute name in _default_form. # # CHILDREN is just Tcl code that can be used to define child DIEs. It # is evaluated in the caller's context. @@ -590,9 +589,25 @@ namespace eval Dwarf { } default { + return "" + } + } + } + + proc _default_form { attr } { + switch -exact -- $attr { + DW_AT_low_pc { + return DW_FORM_addr + } + DW_AT_producer - + DW_AT_comp_dir - + DW_AT_linkage_name - + DW_AT_MIPS_linkage_name - + DW_AT_name { return DW_FORM_string } } + return "" } # Map NAME to its canonical form. @@ -692,11 +707,13 @@ namespace eval Dwarf { _guess_form $attr_value attr_value } } else { - # If the value looks like an integer, a form is required. - if [string is integer $attr_value] { - error "Integer value requires a form" - } set attr_form [_guess_form $attr_value attr_value] + if { $attr_form eq "" } { + set attr_form [_default_form $attr_name] + } + if { $attr_form eq "" } { + error "No form for $attr_name $attr_value" + } } set attr_form [_map_name $attr_form _FORM] -- 2.30.2