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0acf8b658c
Consider the following code, compiled at -O2 on ppc-linux:
procedure Increment (Val : in out Float; Msg : String);
The implementation does not really matter in this case). In our example,
this function is being called from a function with Param_1 set to 99.0.
Trying to break inside that function, and running until reaching that
breakpoint yields:
(gdb) b increment
Breakpoint 1 at 0x100014b4: file callee.adb, line 6.
(gdb) run
Starting program: /[...]/foo
Breakpoint 1, callee.increment (val=99.0, val@entry=0.0, msg=...)
at callee.adb:6
6 if Val > 200.0 then
The @entry value for parameter "val" is incorrect, it should be 99.0.
The associated call-site parameter DIE looks like this:
.uleb128 0xc # (DIE (0x115) DW_TAG_GNU_call_site_parameter)
.byte 0x2 # DW_AT_location
.byte 0x90 # DW_OP_regx
.uleb128 0x21
.byte 0x3 # DW_AT_GNU_call_site_value
.byte 0xf5 # DW_OP_GNU_regval_type
.uleb128 0x3f
.uleb128 0x25
The DW_AT_GNU_call_site_value uses a DW_OP_GNU_regval_type
operation, referencing register 0x3f=63, which is $f31,
an 8-byte floating register. In that register, the value is
stored using the usual 8-byte float format:
(gdb) info float
f31 99.0 (raw 0x4058c00000000000)
The current code evaluating DW_OP_GNU_regval_type operations
currently is (dwarf2expr.c:execute_stack_op):
result = (ctx->funcs->read_reg) (ctx->baton, reg);
result_val = value_from_ulongest (address_type, result);
result_val = value_from_contents (type,
value_contents_all (result_val));
What the ctx->funcs->read_reg function does is read the contents
of the register as if it contained an address. The rest of the code
continues that assumption, thinking it's OK to then use that to
create an address/ulongest struct value, which we then re-type
to the type specified by DW_OP_GNU_regval_type.
We're getting 0.0 above because the read_reg implementations
end up treating the contents of the FP register as an integral,
reading only 4 out of the 8 bytes. Being a big-endian target,
we read the high-order ones, which gives us zero.
This patch fixes the problem by introducing a new callback to
read the contents of a register as a given type, and then adjust
the handling of DW_OP_GNU_regval_type to use that new callback.
gdb/ChangeLog:
* dwarf2expr.h (struct dwarf_expr_context_funcs) <read_reg>:
Extend the documentation a bit.
<get_reg_value>: New field.
* dwarf2loc.c (dwarf_expr_get_reg_value)
(needs_frame_get_reg_value): New functions.
(dwarf_expr_ctx_funcs, needs_frame_ctx_funcs): Add "get_reg_value"
callback.
* dwarf2-frame.c (get_reg_value): New function.
(dwarf2_frame_ctx_funcs): Add "get_reg_value" callback.
* dwarf2expr.c (execute_stack_op) <DW_OP_GNU_regval_type>:
Use new callback to compute result_val.
gdb/testsuite/ChangeLog:
* gdb.ada/O2_float_param: New testcase.
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| bfd | ||
| binutils | ||
| config | ||
| cpu | ||
| elfcpp | ||
| etc | ||
| gas | ||
| gdb | ||
| gold | ||
| gprof | ||
| include | ||
| intl | ||
| ld | ||
| libdecnumber | ||
| libiberty | ||
| opcodes | ||
| readline | ||
| sim | ||
| texinfo | ||
| .cvsignore | ||
| .gitignore | ||
| ChangeLog | ||
| compile | ||
| config-ml.in | ||
| config.guess | ||
| config.rpath | ||
| config.sub | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING3 | ||
| COPYING3.LIB | ||
| COPYING.LIB | ||
| COPYING.LIBGLOSS | ||
| COPYING.NEWLIB | ||
| depcomp | ||
| djunpack.bat | ||
| install-sh | ||
| libtool.m4 | ||
| lt~obsolete.m4 | ||
| ltgcc.m4 | ||
| ltmain.sh | ||
| ltoptions.m4 | ||
| ltsugar.m4 | ||
| ltversion.m4 | ||
| MAINTAINERS | ||
| Makefile.def | ||
| Makefile.in | ||
| Makefile.tpl | ||
| makefile.vms | ||
| missing | ||
| mkdep | ||
| mkinstalldirs | ||
| move-if-change | ||
| README | ||
| README-maintainer-mode | ||
| setup.com | ||
| src-release | ||
| symlink-tree | ||
| ylwrap | ||
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.