[PR gdb/19893] Fix handling of synthetic C++ references
authorMartin Galvan <martin.galvan@tallertechnologies.com>
Tue, 31 May 2016 18:54:01 +0000 (15:54 -0300)
committerMartin Galvan <martin.galvan@tallertechnologies.com>
Tue, 31 May 2016 18:56:34 +0000 (15:56 -0300)
commit3326303bf5ae4c92f2fbbff387ce231a16c1c8bf
tree6003faaf0747941817afc8d62f9f2a0bffcd3802
parentf7433f011ef27838551aded73b8666a86d26b8ec
[PR gdb/19893] Fix handling of synthetic C++ references

https://sourceware.org/bugzilla/show_bug.cgi?id=19893

I've traced the main source of the problem to pieced_value_funcs.coerce_ref not being
implemented. Since gdb always assumes references are implemented as pointers, this
causes it to think that it's dealing with a NULL pointer, thus breaking any operations
involving synthetic references.

What I did here was implementing pieced_value_funcs.coerce_ref using some of the synthetic
pointer handling code from indirect_pieced_value, as Pedro suggested. I also made a few
adjustments to the reference printing code so that it correctly shows either the address
of the referenced value or (if it's non-addressable) the "<synthetic pointer>" string.

I also wrote some unit tests based on Dwarf::assemble; these took a while to make
because in most cases I needed a synthetic reference to a physical variable. Additionally,
I started working on a unit test for classes that have a vtable, but ran into a few issues
so that'll probably go in a future patch. One thing that should definitely be fixed is that
proc function_range (called for MACRO_AT_func) will always try to compile/link using gcc
with the default options instead of g++, thus breaking C++ compilations that require e.g. libstdc++.

gdb/ChangeLog:

* dwarf2loc.c (coerce_pieced_ref, indirect_synthetic_pointer,
fetch_const_value_from_synthetic_pointer): New functions.
(indirect_pieced_value): Move lower half to indirect_synthetic_pointer.
(pieced_value_funcs): Implement coerce_ref.
* valops.c (value_addr): Call coerce_ref for synthetic references.
* valprint.c (valprint_check_validity): Return true for synthetic
references.  Also, don't show "<synthetic pointer>" if they reference
addressable values.
(generic_val_print_ref): Handle synthetic references.  Also move some
code to print_ref_address.
(print_ref_address, get_value_addr_contents): New functions.

gdb/testsuite/ChangeLog:

* gdb.dwarf2/implref.exp: Rename to...
* gdb.dwarf2/implref-const.exp: ...this.  Also add more test statements.
* gdb.dwarf2/implref-array.c: New file.
* gdb.dwarf2/implref-array.exp: Likewise.
* gdb.dwarf2/implref-global.c: Likewise.
* gdb.dwarf2/implref-global.exp: Likewise.
* gdb.dwarf2/implref-struct.c: Likewise.
* gdb.dwarf2/implref-struct.exp: Likewise.
13 files changed:
gdb/ChangeLog
gdb/dwarf2loc.c
gdb/testsuite/ChangeLog
gdb/testsuite/gdb.dwarf2/implref-array.c [new file with mode: 0644]
gdb/testsuite/gdb.dwarf2/implref-array.exp [new file with mode: 0644]
gdb/testsuite/gdb.dwarf2/implref-const.exp [new file with mode: 0644]
gdb/testsuite/gdb.dwarf2/implref-global.c [new file with mode: 0644]
gdb/testsuite/gdb.dwarf2/implref-global.exp [new file with mode: 0644]
gdb/testsuite/gdb.dwarf2/implref-struct.c [new file with mode: 0644]
gdb/testsuite/gdb.dwarf2/implref-struct.exp [new file with mode: 0644]
gdb/testsuite/gdb.dwarf2/implref.exp [deleted file]
gdb/valops.c
gdb/valprint.c