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From: "cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org> To: gdb-prs@sourceware.org Subject: [Bug symtab/25695] abstract and concrete variable listed both with "info locals" Date: Wed, 14 Apr 2021 16:57:59 +0000 [thread overview] Message-ID: <bug-25695-4717-nTRyO4o1J8@http.sourceware.org/bugzilla/> (raw) In-Reply-To: <bug-25695-4717@http.sourceware.org/bugzilla/> https://sourceware.org/bugzilla/show_bug.cgi?id=25695 --- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Tankut Baris Aktemur <aktemur@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=34dc0f95968f835d4c4ac01373de63dec2902c70 commit 34dc0f95968f835d4c4ac01373de63dec2902c70 Author: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com> Date: Mon Feb 8 16:48:39 2021 +0100 gdb/dwarf2: fix "info locals" for clang-compiled inlined functions GDB reports duplicate local vars with "<optimized out>" values for inlined functions that are compiled with Clang. Suppose we have __attribute__((always_inline)) static void aFunction() { int a = 42; if(a > 2) { int value = a; value += 10; /* break here */ } } The "info locals" command at the "break here" line gives the following output: ... Breakpoint 1, aFunction () at test.c:6 6 value += 10; /* break here */ (gdb) info locals value = 42 a = 42 value = <optimized out> (gdb) The reason is, inlined functions that are compiled by Clang do not contain DW_AT_abstract_origin attributes in the DW_TAG_lexical_block entries. See https://bugs.llvm.org/show_bug.cgi?id=49953 E.g. the DIE of the inlined function above is 0x00000087: DW_TAG_inlined_subroutine DW_AT_abstract_origin (0x0000002a "aFunction") DW_AT_low_pc (0x00000000004004b2) DW_AT_high_pc (0x00000000004004d2) DW_AT_call_file ("/tmp/test.c") DW_AT_call_line (11) DW_AT_call_column (0x03) 0x0000009b: DW_TAG_variable DW_AT_location (DW_OP_fbreg -4) DW_AT_abstract_origin (0x00000032 "a") 0x000000a3: DW_TAG_lexical_block DW_AT_low_pc (0x00000000004004c3) DW_AT_high_pc (0x00000000004004d2) 0x000000b0: DW_TAG_variable DW_AT_location (DW_OP_fbreg -8) DW_AT_abstract_origin (0x0000003e "value") This causes GDB to fail matching the concrete lexical scope with the corresponding abstract entry. Hence, the local vars of the abstract function that are contained in the lexical scope are read separately (and thus, in addition to) the local vars of the concrete scope. Because the abstract definitions of the vars do not contain location information, we see the extra 'value = <optimized out>' above. This bug is highly related to PR gdb/25695, but the root cause is not exactly the same. In PR gdb/25695, GCC emits an extra DW_TAG_lexical_block without an DW_AT_abstract_origin that wraps the body of the inlined function. That is, the trees of the abstract DIE for the function and its concrete instance are structurally not the same. In the case of using Clang, the trees have the same structure. To tackle the Clang case, when traversing the children of the concrete instance root, keep a reference to the child of the abstract DIE that corresponds to the concrete child, so that we can match the two DIEs heuristically in case of missing DW_AT_abstract_origin attributes. The updated gdb.opt/inline-locals.exp test has been checked with GCC 5-10 and Clang 5-11. gdb/ChangeLog: 2021-04-14 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com> * dwarf2/read.c (inherit_abstract_dies): Keep a reference to the corresponding child of the abstract DIE when iterating the children of the concrete DIE. gdb/testsuite/ChangeLog: 2021-04-14 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com> * gdb.opt/inline-locals.c (scoped): New function. (main): Call 'scoped'. * gdb.opt/inline-locals.exp: Update with "info locals" tests for scoped variables. * gdb.dwarf2/dw2-inline-with-lexical-scope.c: New file. * gdb.dwarf2/dw2-inline-with-lexical-scope.exp: New file. -- You are receiving this mail because: You are on the CC list for the bug.
prev parent reply other threads:[~2021-04-14 16:57 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-03-18 22:46 [Bug symtab/25695] New: " vries at gcc dot gnu.org 2020-03-18 22:46 ` [Bug symtab/25695] " vries at gcc dot gnu.org 2021-04-14 16:57 ` cvs-commit at gcc dot gnu.org [this message]
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