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Avoid crash on missing dwz file

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If DWARF contains a reference to a "dwz" file, but there is no
.gnu_debugaltlink section, then gdb will crash.  This happens because
dwarf2_get_dwz_file will return NULL, but some callers do not expect
this.

This patch changes dwarf2_get_dwz_file so that callers can require a
dwz file.  Then, it updates the callers that are attempting to process
references to the dwz file to require one.

This includes a new testcase.  The dwarf.exp changes don't handle the
new forms exactly correctly -- they are only handled well enough to
let this test case complete.

gdb/ChangeLog
2021-03-06  Tom Tromey  <tom@tromey.com>

	* dwarf2/read.h (dwarf2_get_dwz_file): Add 'require' parameter.
	* dwarf2/read.c (dwarf2_get_dwz_file): Add 'require' parameter.
	(get_abbrev_section_for_cu, read_attribute_value)
	(get_debug_line_section): Update.
	* dwarf2/macro.c (dwarf_decode_macro_bytes): Update.

gdb/testsuite/ChangeLog
2021-03-06  Tom Tromey  <tom@tromey.com>

	* lib/dwarf.exp (_handle_DW_FORM): Treat DW_FORM_GNU_ref_alt and
	DW_FORM_GNU_strp_alt like DW_FORM_sec_offset.
	* gdb.dwarf2/dwznolink.exp: New file.
This commit is contained in:
Tom Tromey
2021-03-06 09:26:39 -07:00
parent fbedd54644
commit a7308ce01e
7 changed files with 96 additions and 13 deletions
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14
gdb/dwarf2/read.c
View File

@@ -2285,7 +2285,7 @@ dwz_search_other_debugdirs (std::string &filename, bfd_byte *buildid,
/* See dwarf2read.h. */
struct dwz_file *
dwarf2_get_dwz_file (dwarf2_per_bfd *per_bfd)
dwarf2_get_dwz_file (dwarf2_per_bfd *per_bfd, bool require)
{
bfd_size_type buildid_len_arg;
size_t buildid_len;
@@ -2301,7 +2301,11 @@ dwarf2_get_dwz_file (dwarf2_per_bfd *per_bfd)
if (data == NULL)
{
if (bfd_get_error () == bfd_error_no_error)
return NULL;
{
if (!require)
return nullptr;
error (_("could not read '.gnu_debugaltlink' section"));
}
error (_("could not read '.gnu_debugaltlink' section: %s"),
bfd_errmsg (bfd_get_error ()));
}
@@ -6308,7 +6312,7 @@ get_abbrev_section_for_cu (struct dwarf2_per_cu_data *this_cu)
dwarf2_per_bfd *per_bfd = this_cu->per_bfd;
if (this_cu->is_dwz)
abbrev = &dwarf2_get_dwz_file (per_bfd)->abbrev;
abbrev = &dwarf2_get_dwz_file (per_bfd, true)->abbrev;
else
abbrev = &per_bfd->abbrev;
@@ -20654,7 +20658,7 @@ read_attribute_value (const struct die_reader_specs *reader,
/* FALLTHROUGH */
case DW_FORM_GNU_strp_alt:
{
dwz_file *dwz = dwarf2_get_dwz_file (per_objfile->per_bfd);
dwz_file *dwz = dwarf2_get_dwz_file (per_objfile->per_bfd, true);
LONGEST str_offset = cu_header->read_offset (abfd, info_ptr,
&bytes_read);
@@ -21252,7 +21256,7 @@ get_debug_line_section (struct dwarf2_cu *cu)
section = &cu->dwo_unit->dwo_file->sections.line;
else if (cu->per_cu->is_dwz)
{
dwz_file *dwz = dwarf2_get_dwz_file (per_objfile->per_bfd);
dwz_file *dwz = dwarf2_get_dwz_file (per_objfile->per_bfd, true);
section = &dwz->line;
}