Fix pr 17276.
See the description here: https://sourceware.org/ml/gdb-patches/2014-08/msg00283.html This patch keeps track of whether the current line has seen a non-zero discriminator, and if so coalesces consecutive entries for the same line (by ignoring all entries after the first). gdb/ChangeLog: PR 17276 * dwarf2read.c (dwarf_record_line_p): New function. (dwarf_decode_lines_1): Ignore subsequent line number entries for the same line if any entry had a non-zero discriminator. gdb/testsuite/ChangeLog: * gdb.dwarf2/dw2-single-line-discriminators.S: New file. * gdb.dwarf2/dw2-single-line-discriminators.c: New file. * gdb.dwarf2/dw2-single-line-discriminators.exp: New file.
This commit is contained in:
Doug Evans
parent
9bda4a968f
commit
a05a36a5fc
6 changed files with 471 additions and 12 deletions
108
gdb/dwarf2read.c
108
gdb/dwarf2read.c
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@ -17174,6 +17174,53 @@ noop_record_line (struct subfile *subfile, int line, CORE_ADDR pc)
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return;
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}
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/* Return non-zero if we should add LINE to the line number table.
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LINE is the line to add, LAST_LINE is the last line that was added,
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LAST_SUBFILE is the subfile for LAST_LINE.
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LINE_HAS_NON_ZERO_DISCRIMINATOR is non-zero if LINE has ever
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had a non-zero discriminator.
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We have to be careful in the presence of discriminators.
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E.g., for this line:
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for (i = 0; i < 100000; i++);
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clang can emit four line number entries for that one line,
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each with a different discriminator.
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See gdb.dwarf2/dw2-single-line-discriminators.exp for an example.
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However, we want gdb to coalesce all four entries into one.
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Otherwise the user could stepi into the middle of the line and
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gdb would get confused about whether the pc really was in the
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middle of the line.
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Things are further complicated by the fact that two consecutive
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line number entries for the same line is a heuristic used by gcc
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to denote the end of the prologue. So we can't just discard duplicate
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entries, we have to be selective about it. The heuristic we use is
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that we only collapse consecutive entries for the same line if at least
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one of those entries has a non-zero discriminator. PR 17276.
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Note: Addresses in the line number state machine can never go backwards
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within one sequence, thus this coalescing is ok. */
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static int
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dwarf_record_line_p (unsigned int line, unsigned int last_line,
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int line_has_non_zero_discriminator,
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struct subfile *last_subfile)
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{
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if (current_subfile != last_subfile)
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return 1;
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if (line != last_line)
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return 1;
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/* Same line for the same file that we've seen already.
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As a last check, for pr 17276, only record the line if the line
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has never had a non-zero discriminator. */
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if (!line_has_non_zero_discriminator)
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return 1;
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return 0;
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}
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/* Use P_RECORD_LINE to record line number LINE beginning at address ADDRESS
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in the line table of subfile SUBFILE. */
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@ -17234,6 +17281,12 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
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int is_stmt = lh->default_is_stmt;
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int end_sequence = 0;
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unsigned char op_index = 0;
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unsigned int discriminator = 0;
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/* The last line number that was recorded, used to coalesce
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consecutive entries for the same line. This can happen, for
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example, when discriminators are present. PR 17276. */
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unsigned int last_line = 0;
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int line_has_non_zero_discriminator = 0;
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if (!decode_for_pst_p && lh->num_file_names >= file)
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{
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@ -17265,6 +17318,7 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
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{
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/* Special opcode. */
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unsigned char adj_opcode;
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int line_delta;
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adj_opcode = op_code - lh->opcode_base;
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address += (((op_index + (adj_opcode / lh->line_range))
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@ -17272,7 +17326,10 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
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* lh->minimum_instruction_length);
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op_index = ((op_index + (adj_opcode / lh->line_range))
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% lh->maximum_ops_per_instruction);
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line += lh->line_base + (adj_opcode % lh->line_range);
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line_delta = lh->line_base + (adj_opcode % lh->line_range);
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line += line_delta;
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if (line_delta != 0)
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line_has_non_zero_discriminator = discriminator != 0;
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if (lh->num_file_names < file || file == 0)
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dwarf2_debug_line_missing_file_complaint ();
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/* For now we ignore lines not starting on an
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@ -17286,13 +17343,19 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
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{
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dwarf_finish_line (gdbarch, last_subfile,
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address, p_record_line);
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last_subfile = current_subfile;
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}
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/* Append row to matrix using current values. */
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dwarf_record_line (gdbarch, current_subfile,
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line, address, p_record_line);
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if (dwarf_record_line_p (line, last_line,
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line_has_non_zero_discriminator,
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last_subfile))
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{
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dwarf_record_line (gdbarch, current_subfile,
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line, address, p_record_line);
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}
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last_subfile = current_subfile;
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last_line = line;
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}
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}
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discriminator = 0;
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}
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else switch (op_code)
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{
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@ -17355,8 +17418,14 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
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break;
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case DW_LNE_set_discriminator:
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/* The discriminator is not interesting to the debugger;
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just ignore it. */
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line_ptr = extended_end;
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just ignore it. We still need to check its value though:
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if there are consecutive entries for the same
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(non-prologue) line we want to coalesce them.
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PR 17276. */
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discriminator = read_unsigned_leb128 (abfd, line_ptr,
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&bytes_read);
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line_has_non_zero_discriminator |= discriminator != 0;
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line_ptr += bytes_read;
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break;
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default:
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complaint (&symfile_complaints,
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@ -17385,12 +17454,19 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
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{
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dwarf_finish_line (gdbarch, last_subfile,
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address, p_record_line);
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last_subfile = current_subfile;
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}
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dwarf_record_line (gdbarch, current_subfile,
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line, address, p_record_line);
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if (dwarf_record_line_p (line, last_line,
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line_has_non_zero_discriminator,
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last_subfile))
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{
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dwarf_record_line (gdbarch, current_subfile,
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line, address, p_record_line);
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}
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last_subfile = current_subfile;
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last_line = line;
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}
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}
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discriminator = 0;
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break;
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case DW_LNS_advance_pc:
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{
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@ -17406,8 +17482,15 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
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}
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break;
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case DW_LNS_advance_line:
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line += read_signed_leb128 (abfd, line_ptr, &bytes_read);
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line_ptr += bytes_read;
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{
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int line_delta
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= read_signed_leb128 (abfd, line_ptr, &bytes_read);
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line += line_delta;
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if (line_delta != 0)
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line_has_non_zero_discriminator = discriminator != 0;
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line_ptr += bytes_read;
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}
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break;
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case DW_LNS_set_file:
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{
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@ -17429,6 +17512,7 @@ dwarf_decode_lines_1 (struct line_header *lh, const char *comp_dir,
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if (!decode_for_pst_p)
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{
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last_subfile = current_subfile;
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line_has_non_zero_discriminator = discriminator != 0;
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dwarf2_start_subfile (fe->name, dir, comp_dir);
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}
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}
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