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d65befc152
This commit implements a fix for a bug reported against GDB on Fedora bugzilla... https://bugzilla.redhat.com/show_bug.cgi?id=2166796 The test case in that bug report involved running gdb against the 'jq' program (which is a command-line JSON processor) on Fedora 37. Since the debug info is compiler (and compile-time option) dependent, it won't necessarily show up in other distributions or even past or future versions of Fedora. (E.g. when trying the example shown below on Fedora 38, GDB says that the value of 'value' has been optimized out. I.e. it does not demonstrate the same DWARF error that can be see when using Fedora 37.) That said, on Fedora 37, the bug could be reproduced as follows: [kev@f37-1 ~]$ gdb jq -q -ex 'b src/util.c:415' -ex 'r </dev/null' Reading symbols from jq... This GDB supports auto-downloading debuginfo from the following URLs: <https://debuginfod.fedoraproject.org/> Enable debuginfod for this session? (y or [n]) y Debuginfod has been enabled. To make this setting permanent, add 'set debuginfod enabled on' to .gdbinit. Reading symbols from /home/kev/.cache/debuginfod_client/9d3c8b4197350a190a74972d481de32abf641aa4/debuginfo... No source file named src/util.c. Make breakpoint pending on future shared library load? (y or [n]) y Breakpoint 1 (src/util.c:415) pending. Starting program: /usr/bin/jq </dev/null [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib64/libthread_db.so.1". Breakpoint 1, jq_util_input_next_input (state=0x55555555d7f0) at src/util.c:416 416 if (state->parser == NULL) { (gdb) p value DWARF-2 expression error: DW_OP_GNU_uninit must always be the very last op. This is undesirable - rather than output an error about the DWARF info, we'd prefer to see a value, even if it is uninitialized. Examination of the debuginfo showed the following: <1><468f1>: Abbrev Number: 112 (DW_TAG_subprogram) <468f2> DW_AT_external : 1 <468f2> DW_AT_name : (indirect string, offset: 0x4781): jq_util_input_next_input <468f6> DW_AT_decl_file : 10 <468f6> DW_AT_decl_line : 411 <468f8> DW_AT_decl_column : 4 <468f9> DW_AT_prototyped : 1 <468f9> DW_AT_type : <0x3f2> <468fd> DW_AT_sibling : <0x4692e> ... <2><46921>: Abbrev Number: 102 (DW_TAG_variable) <46922> DW_AT_name : (indirect string, offset: 0x8cb): value <46926> DW_AT_decl_file : 10 <46926> DW_AT_decl_line : 414 <46928> DW_AT_decl_column : 6 <46929> DW_AT_type : <0x3f2> Note that there's no DW_AT_location, so I looked for an abstract origin entry: <2><2dfa0>: Abbrev Number: 90 (DW_TAG_variable) <2dfa1> DW_AT_abstract_origin: <0x46921> <2dfa5> DW_AT_location : 0x27cf1 (location list) <2dfa9> DW_AT_GNU_locviews: 0x27ce1 (Note that the DW_AT_abstract_origin attribute's value is 0x46921 which is the DIE for the local variable "value".) Looking at the location list, I see: 00027cf1 v000000000000000 v000000000000000 views at 00027ce1 for: 000000000002f8fe 000000000002f92e (DW_OP_reg13 (r13); DW_OP_GNU_uninit; DW_OP_piece: 8; DW_OP_reg12 (r12); DW_OP_GNU_uninit; DW_OP_piece: 8) While DW_OP_GNU_uninit is not the very last op, it is the last op prior to DW_OP_piece. The fix involved changing the DW_OP_GNU_uninit case in dwarf_expr_context::execute_stack_op in gdb/dwarf2/expr.c so that DW_OP_GNU_uninit may appear just before DW_OP_piece. With the fix in place, attempting to print 'value' now looks like this: (gdb) p value $1 = [uninitialized] {kind_flags = 0 '\000', pad_ = 0 '\000', offset = 0, size = 0, u = {ptr = 0x0, number = 0}} Note that "[uninitialized]" is part of the output. (But also note that there's an extra space character.) I've made a new test case, gdb.dwarf2/DW_OP_piece_with_DW_OP_GNU_uninit.exp, by adapting an existing one, gdb.dwarf2/opt-out-not-implptr.exp. Since it uses the DWARF assembler, the test case does not depend on a specific compiler version or compiler options. Tested on Fedora 37 and Fedora 38. |
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| .. | ||
| abbrev-cache.c | ||
| abbrev-cache.h | ||
| abbrev.c | ||
| abbrev.h | ||
| ada-imported.c | ||
| attribute.c | ||
| attribute.h | ||
| call-site.h | ||
| comp-unit-head.c | ||
| comp-unit-head.h | ||
| cooked-index.c | ||
| cooked-index.h | ||
| cu.c | ||
| cu.h | ||
| die.c | ||
| die.h | ||
| dwz.c | ||
| dwz.h | ||
| expr.c | ||
| expr.h | ||
| file-and-dir.h | ||
| frame-tailcall.c | ||
| frame-tailcall.h | ||
| frame.c | ||
| frame.h | ||
| index-cache.c | ||
| index-cache.h | ||
| index-common.c | ||
| index-common.h | ||
| index-write.c | ||
| index-write.h | ||
| leb.c | ||
| leb.h | ||
| line-header.c | ||
| line-header.h | ||
| loc.c | ||
| loc.h | ||
| macro.c | ||
| macro.h | ||
| mapped-index.h | ||
| public.h | ||
| read-debug-names.c | ||
| read-debug-names.h | ||
| read-gdb-index.c | ||
| read-gdb-index.h | ||
| read.c | ||
| read.h | ||
| sect-names.h | ||
| section.c | ||
| section.h | ||
| stringify.c | ||
| stringify.h | ||
| tag.h | ||
| types.h | ||