From 4cf88725da1cb503be04d3237354105ec170bc86 Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Fri, 7 May 2021 12:13:05 +0200 Subject: [PATCH] [gdb/symtab] Fix infinite recursion in dwarf2_cu::get_builder() With the test-case attached in PR26327, gdb aborts: ... $ gdb -q -batch 447.dealII -ex "b main" Aborted (core dumped) ... when running out of stack due to infinite recursion: ... #8 0x00000000006aaba6 in dwarf2_cu::get_builder (this=0x35e4b40) at src/gdb/dwarf2/read.c:700 #9 0x00000000006aaba6 in dwarf2_cu::get_builder (this=0x22ee2c0) at src/gdb/dwarf2/read.c:700 #10 0x00000000006aaba6 in dwarf2_cu::get_builder (this=0x35e4b40) at src/gdb/dwarf2/read.c:700 #11 0x00000000006aaba6 in dwarf2_cu::get_builder (this=0x22ee2c0) at src/gdb/dwarf2/read.c:700 ... We're recursing in this code in dwarf2_cu::get_builder(): ... /* Otherwise, search ancestors for a valid builder. */ if (ancestor != nullptr) return ancestor->get_builder (); ... due to the fact that the ancestor chain is a cycle. Higher up in the call stack, we find some code that is responsible for triggering this, in new_symbol: ... case DW_TAG_formal_parameter: { /* If we are inside a function, mark this as an argument. If not, we might be looking at an argument to an inlined function when we do not have enough information to show inlined frames; pretend it's a local variable in that case so that the user can still see it. */ struct context_stack *curr = cu->get_builder ()->get_current_context_stack (); if (curr != nullptr && curr->name != nullptr) SYMBOL_IS_ARGUMENT (sym) = 1; ... This is code that was added to support pre-4.1 gcc, to be able to show arguments of inlined functions as locals, in the absense of sufficiently correct debug information. Removing this code (that is, doing SYMBOL_IS_ARGUMENT (sym) = 1 unconditially), fixes the crash. The ancestor variable also seems to have been added specifically to deal with fallout from this code, so remove that as well. Tested on x86_64-linux: - openSUSE Leap 15.2 with gcc 7.5.0, and - openSUSE Tumbleweed with gcc 10.3.0. gdb/ChangeLog: 2021-05-07 Tom de Vries PR symtab/26327 * dwarf2/read.c (struct dwarf2_cu): Remove ancestor. (dwarf2_cu::get_builder): Remove ancestor-related code. (new_symbol): Remove code supporting pre-4.1 gcc that show arguments of inlined functions as locals. (follow_die_offset, follow_die_sig_1): Remove setting of ancestor. gdb/doc/ChangeLog: 2021-05-07 Tom de Vries PR symtab/26327 * gdb.texinfo (Inline Functions): Update. --- gdb/ChangeLog | 9 +++++++++ gdb/doc/ChangeLog | 5 +++++ gdb/doc/gdb.texinfo | 4 ++-- gdb/dwarf2/read.c | 25 ++----------------------- 4 files changed, 18 insertions(+), 25 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 4e57a1628ed..70d4972cd52 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,12 @@ +2021-05-07 Tom de Vries + + PR symtab/26327 + * dwarf2/read.c (struct dwarf2_cu): Remove ancestor. + (dwarf2_cu::get_builder): Remove ancestor-related code. + (new_symbol): Remove code supporting pre-4.1 gcc that show arguments + of inlined functions as locals. + (follow_die_offset, follow_die_sig_1): Remove setting of ancestor. + 2021-05-07 Andrew Burgess * guile/guile-internal.h (gdbscm_safe_source_script): Change diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog index d64504f1ffc..a56735896c5 100644 --- a/gdb/doc/ChangeLog +++ b/gdb/doc/ChangeLog @@ -1,3 +1,8 @@ +2021-05-07 Tom de Vries + + PR symtab/26327 + * gdb.texinfo (Inline Functions): Update. + 2021-05-06 Tankut Baris Aktemur * gdb.texinfo (GDB/MI Breakpoint Commands): Mention the diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index 56f37eb2288..f4d7085da58 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -13842,8 +13842,8 @@ when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1 do not emit two required attributes (@samp{DW_AT_call_file} and @samp{DW_AT_call_line}); @value{GDBN} does not display inlined function calls with earlier versions of @value{NGCC}. It instead -displays the arguments and local variables of inlined functions as -local variables in the caller. +displays local variables of inlined functions as local variables in +the caller. The body of an inlined function is directly included at its call site; unlike a non-inlined function, there are no instructions devoted to diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c index 5796cf1730b..b2f48f1f395 100644 --- a/gdb/dwarf2/read.c +++ b/gdb/dwarf2/read.c @@ -684,10 +684,6 @@ public: struct partial_die_info *find_partial_die (sect_offset sect_off); - /* If this CU was inherited by another CU (via specification, - abstract_origin, etc), this is the ancestor CU. */ - dwarf2_cu *ancestor; - /* Get the buildsym_compunit for this CU. */ buildsym_compunit *get_builder () { @@ -695,10 +691,6 @@ public: if (m_builder != nullptr) return m_builder.get (); - /* Otherwise, search ancestors for a valid builder. */ - if (ancestor != nullptr) - return ancestor->get_builder (); - return nullptr; } }; @@ -22045,15 +22037,7 @@ new_symbol (struct die_info *die, struct type *type, struct dwarf2_cu *cu, break; case DW_TAG_formal_parameter: { - /* If we are inside a function, mark this as an argument. If - not, we might be looking at an argument to an inlined function - when we do not have enough information to show inlined frames; - pretend it's a local variable in that case so that the user can - still see it. */ - struct context_stack *curr - = cu->get_builder ()->get_current_context_stack (); - if (curr != nullptr && curr->name != nullptr) - SYMBOL_IS_ARGUMENT (sym) = 1; + SYMBOL_IS_ARGUMENT (sym) = 1; attr = dwarf2_attr (die, DW_AT_location, cu); if (attr != nullptr) { @@ -23389,9 +23373,6 @@ follow_die_offset (sect_offset sect_off, int offset_in_dwz, *ref_cu = target_cu; temp_die.sect_off = sect_off; - if (target_cu != cu) - target_cu->ancestor = cu; - return (struct die_info *) htab_find_with_hash (target_cu->die_hash, &temp_die, to_underlying (sect_off)); @@ -23741,7 +23722,7 @@ follow_die_sig_1 (struct die_info *src_die, struct signatured_type *sig_type, struct dwarf2_cu **ref_cu) { struct die_info temp_die; - struct dwarf2_cu *sig_cu, *cu = *ref_cu; + struct dwarf2_cu *sig_cu; struct die_info *die; dwarf2_per_objfile *per_objfile = (*ref_cu)->per_objfile; @@ -23777,8 +23758,6 @@ follow_die_sig_1 (struct die_info *src_die, struct signatured_type *sig_type, } *ref_cu = sig_cu; - if (sig_cu != cu) - sig_cu->ancestor = cu; return die; } -- 2.30.2