Created attachment 6645 [details] An x86-64 assembler test file for this bug. Raising defect as requested in this gdb-patches mailing list thread: http://sourceware.org/ml/gdb-patches/2012-08/msg00715.html This bug is for a failure in the test gdb.dwarf2/dw2-op-out-param.exp that was added at the end of the above mailing list thread. If a variable is described by the DWARF as being split over multiple registers using DWARF piece information, but some of those register are marked as optimised out by a later frame then gdb incorrectly believes the value of those pieces is zero. Having a variable help in a register that is marked as optimised out by a later frame should probably be fixed in the dwarf producer, however, it is interesting in this case that gdb, without error or warning displays the *wrong* answer. However, no example of this bug has yet been seen in the wild. The test creates two call stacks: main --> struct_param_two_reg_pieces --> breakpt main --> int_param_two_reg_pieces --> breakpt In each function "struct_param_two_reg_pieces" and "int_param_two_reg_pieces" variables are placed in multiple register using piece information, and the function "breakpt" marks some of these registers as optimised out. The test file is x86-64 specific, download test.S, and assemble as: gcc -o test test.S Then run gdb as: > gdb test (gdb) break breakpt Breakpoint 1 at 0x4004fb (gdb) r Starting program: /projects/firepath_work/aburgess/tmp/gdb/test warning: no loadable sections found in added symbol-file system-supplied DSO at 0x2aaaaaaab000 Breakpoint 1, 0x00000000004004fb in breakpt () (gdb) c Continuing. Breakpoint 1, 0x00000000004004fb in breakpt () (gdb) c Continuing. Breakpoint 1, 0x00000000004004fb in breakpt () (gdb) set output-radix 16 Output radix now set to decimal 16, hex 10, octal 20. (gdb) set print frame-arguments all (gdb) bt #0 0x00000000004004fb in breakpt () #1 0x000000000040052e in struct_param_two_reg_pieces (operand0= {a = 0xdeadbe04deadbe05, b = 0x0}, operand1= {a = 0x0, b = 0xdeadbe00deadbe01}, operand2={a = 0x0, b = 0x0}) #2 0x00000000004004ef in main () (gdb) c Continuing. Breakpoint 1, 0x00000000004004fb in breakpt () (gdb) bt #0 0x00000000004004fb in breakpt () #1 0x000000000040053e in int_param_two_reg_pieces (operand0=0xdeadbe05, operand1=0xdeadbe0100000000, operand2=0x0) #2 0x00000000004004f5 in main () (gdb) quit ## END ## In both backtraces the values for operand0, operand1, and operand2 are wrong. In the first backtrace the correct values are: operand0={a = 0xdeadbe04deadbe05, b = <optimized out>} operand1={a = <optimized out>, b = 0xdeadbe00deadbe01} operand2=<optimized out> In the second backtrace the correct values are: operand0=<optimized out> operand1=<optimized out> operand2=<optimized out> In the second case we must mark the whole value as optimised out as the variable is an integer type, I can't imagine how we'd show a partially optimised out integer variable.
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The branch, master has been updated via 9a0dc9e3699018b15980bb6a39eb33dea8fefa34 (commit) from 6694c4110a37bc951d01132d6e56445d57350627 (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=9a0dc9e3699018b15980bb6a39eb33dea8fefa34 commit 9a0dc9e3699018b15980bb6a39eb33dea8fefa34 Author: Pedro Alves <palves@redhat.com> Date: Wed Aug 20 00:07:40 2014 +0100 Handle partially optimized out values similarly to unavailable values This fixes PR symtab/14604, PR symtab/14605, and Jan's test at https://sourceware.org/ml/gdb-patches/2014-07/msg00158.html, in a tree with bddbbed reverted: 2014-07-22 Pedro Alves <palves@redhat.com> * value.c (allocate_optimized_out_value): Don't mark value as non-lazy. The PRs are about variables described by the DWARF as being split over multiple registers using DWARF piece information, but some of those registers being marked as optimised out (not saved) by a later frame. GDB currently incorrectly mishandles these partially-optimized-out values. Even though we can usually tell from the debug info whether a local or global is optimized out, handling the case of a local living in a register that was not saved in a frame requires fetching the variable. GDB also needs to fetch a value to tell whether parts of it are "<unavailable>". Given this, it's not worth it to try to avoid fetching lazy optimized-out values based on debug info alone. So this patch makes GDB track which chunks of a value's contents are optimized out like it tracks <unavailable> contents. That is, it makes value->optimized_out be a bit range vector instead of a boolean, and removes the struct lval_funcs check_validity and check_any_valid hooks. Unlike Andrew's series which this is based on (at https://sourceware.org/ml/gdb-patches/2013-08/msg00300.html, note some pieces have gone in since), this doesn't merge optimized out and unavailable contents validity/availability behind a single interface, nor does it merge the bit range vectors themselves (at least yet). While it may be desirable to have a single entry point that returns existence of contents irrespective of what may make them invalid/unavailable, several places want to treat optimized out / unavailable / etc. differently, so each spot that potentially could use it will need to be careful considered on case-by-case basis, and best done as a separate change. This fixes Jan's test, because value_available_contents_eq wasn't considering optimized out value contents. It does now, and because of that it's been renamed to value_contents_eq. A new intro comment is added to value.h describing "<optimized out>", "<not saved>" and "<unavailable>" values. gdb/ PR symtab/14604 PR symtab/14605 * ada-lang.c (coerce_unspec_val_to_type): Use value_contents_copy_raw. * ada-valprint.c (val_print_packed_array_elements): Adjust. * c-valprint.c (c_val_print): Use value_bits_any_optimized_out. * cp-valprint.c (cp_print_value_fields): Let the common printing code handle optimized out values. (cp_print_value_fields_rtti): Use value_bits_any_optimized_out. * d-valprint.c (dynamic_array_type): Use value_bits_any_optimized_out. * dwarf2loc.c (entry_data_value_funcs): Remove check_validity and check_any_valid fields. (check_pieced_value_bits): Delete and inline ... (check_pieced_synthetic_pointer): ... here. (check_pieced_value_validity): Delete. (check_pieced_value_invalid): Delete. (pieced_value_funcs): Remove check_validity and check_any_valid fields. (read_pieced_value): Use mark_value_bits_optimized_out. (write_pieced_value): Switch to use mark_value_bytes_optimized_out. (dwarf2_evaluate_loc_desc_full): Copy the value contents instead of assuming the whole value is optimized out. * findvar.c (read_frame_register_value): Remove special handling of optimized out registers. (value_from_register): Use mark_value_bytes_optimized_out. * frame-unwind.c (frame_unwind_got_optimized): Use mark_value_bytes_optimized_out. * jv-valprint.c (java_value_print): Adjust. (java_print_value_fields): Let the common printing code handle optimized out values. * mips-tdep.c (mips_print_register): Remove special handling of optimized out registers. * opencl-lang.c (lval_func_check_validity): Delete. (lval_func_check_any_valid): Delete. (opencl_value_funcs): Remove check_validity and check_any_valid fields. * p-valprint.c (pascal_object_print_value_fields): Let the common printing code handle optimized out values. * stack.c (read_frame_arg): Remove special handling of optimized out values. Fetch both VAL and ENTRYVAL before comparing contents. Adjust to value_available_contents_eq rename. * valprint.c (valprint_check_validity) (val_print_scalar_formatted): Use value_bits_any_optimized_out. (val_print_array_elements): Adjust. * value.c (struct value) <optimized_out>: Now a VEC(range_s). (value_bits_any_optimized_out): New function. (value_entirely_covered_by_range_vector): New function, factored out from value_entirely_unavailable. (value_entirely_unavailable): Reimplement. (value_entirely_optimized_out): New function. (insert_into_bit_range_vector): New function, factored out from mark_value_bits_unavailable. (mark_value_bits_unavailable): Reimplement. (struct ranges_and_idx): New struct. (find_first_range_overlap_and_match): New function, factored out from value_available_contents_bits_eq. (value_available_contents_bits_eq): Rename to ... (value_contents_bits_eq): ... this. Check both unavailable contents and optimized out contents. (value_available_contents_eq): Rename to ... (value_contents_eq): ... this. (allocate_value_lazy): Remove reference to the old optimized_out boolean. (allocate_optimized_out_value): Use mark_value_bytes_optimized_out. (require_not_optimized_out): Adjust to check whether the optimized_out vec is empty. (ranges_copy_adjusted): New function, factored out from value_contents_copy_raw. (value_contents_copy_raw): Also copy the optimized out ranges. Assert the destination ranges aren't optimized out. (value_contents_copy): Update comment, remove call to require_not_optimized_out. (value_contents_equal): Adjust to check whether the optimized_out vec is empty. (set_value_optimized_out, value_optimized_out_const): Delete. (mark_value_bytes_optimized_out, mark_value_bits_optimized_out): New functions. (value_entirely_optimized_out, value_bits_valid): Delete. (value_copy): Take a VEC copy of the 'optimized_out' field. (value_primitive_field): Remove special handling of optimized out. (value_fetch_lazy): Assert that lazy values have no unavailable regions. Use value_bits_any_optimized_out. Remove some special handling for optimized out values. * value.h: Add intro comment about <optimized out> and <unavailable>. (struct lval_funcs): Remove check_validity and check_any_valid fields. (set_value_optimized_out, value_optimized_out_const): Remove. (mark_value_bytes_optimized_out, mark_value_bits_optimized_out): New declarations. (value_bits_any_optimized_out): New declaration. (value_bits_valid): Delete declaration. (value_available_contents_eq): Rename to ... (value_contents_eq): ... this, and extend comments. gdb/testsuite/ PR symtab/14604 PR symtab/14605 * gdb.dwarf2/dw2-op-out-param.exp: Remove kfail branches and use gdb_test. ----------------------------------------------------------------------- Summary of changes: gdb/ChangeLog | 101 ++++++ gdb/ada-lang.c | 4 +- gdb/ada-valprint.c | 6 +- gdb/c-valprint.c | 6 +- gdb/cp-valprint.c | 11 +- gdb/d-valprint.c | 5 +- gdb/dwarf2loc.c | 81 +---- gdb/findvar.c | 8 +- gdb/frame-unwind.c | 2 +- gdb/jv-valprint.c | 13 +- gdb/mips-tdep.c | 6 - gdb/opencl-lang.c | 54 --- gdb/p-valprint.c | 5 - gdb/stack.c | 17 +- gdb/testsuite/ChangeLog | 8 + gdb/testsuite/gdb.dwarf2/dw2-op-out-param.exp | 30 +-- gdb/valprint.c | 22 +- gdb/value.c | 467 +++++++++++++++---------- gdb/value.h | 158 ++++++--- 19 files changed, 554 insertions(+), 450 deletions(-)
Fixed.