[08/10] Use the linkage name if it exists

Message ID 20200325200715.12947-9-tom@tromey.com
State New
Headers show
Series
  • Fix two name-related bugs in DWARF reader
Related show

Commit Message

Tom Tromey March 25, 2020, 8:07 p.m.
The DWARF reader has had some odd code since the "physname" patches landed.

In particular, these patches caused PR symtab/12707; namely, they made
it so "set print demangle off" no longer works.

This patch attempts to fix the problem.  It arranges to store the
linkage name on the symbol if it exists, and it changes the DWARF
reader so that the demangled name is no longer (usually) stored in the
symbol's "linkage name" field.

c-linkage-name.exp needed a tweak, because it started working
correctly.  This conforms to what I think ought to happen, so this
seems like an improvement here.

compile-object-load.c needed a small change to use
symbol_matches_search_name rather than directly examining the linkage
name.  Looking directly at the name does the wrong thing for C++.

There is still some name-related confusion in the DWARF reader:

* "physname" often refers to the logical name and not what I would
  consider to be the "physical" name;

* dwarf2_full_name, dwarf2_name, and dwarf2_physname all exist and
  return different strings -- but this seems like at least one name
  too many.  For example, Fortran requires dwarf2_full_name, but other
  languages do not.

* To my surprise, dwarf2_physname prefers the form emitted by the
  demangler over the one that it computes.  This seems backward to me,
  given that the partial symbol reader prefers the opposite, and it
  seems to me that this choice may perform better as well.

I didn't attempt to clean up these things.  It would be good to do,
but whenever I contemplate it I get caught up in dreams of truly
rewriting the DWARF reader instead.

gdb/ChangeLog
2020-03-25  Tom Tromey  <tom@tromey.com>

	PR symtab/12707:
	* dwarf2/read.c (add_partial_symbol): Use the linkage name if it
	exists.
	(new_symbol): Likewise.
	* compile/compile-object-load.c (get_out_value_type): Use
	symbol_matches_search_name.

gdb/testsuite/ChangeLog
2020-03-25  Tom Tromey  <tom@tromey.com>

	PR symtab/12707:
	* gdb.python/py-symbol.exp: Update expected results for
	linkage_name test.
	* gdb.cp/print-demangle.exp: New file.
	* gdb.base/c-linkage-name.exp: Fix test.
	* gdb.guile/scm-symbol.exp: Update expected results for
	linkage_name test.
---
 gdb/ChangeLog                             |  9 +++++++
 gdb/compile/compile-object-load.c         |  7 ++---
 gdb/dwarf2/read.c                         | 29 ++++++++++++++------
 gdb/testsuite/ChangeLog                   | 10 +++++++
 gdb/testsuite/gdb.base/c-linkage-name.exp |  2 +-
 gdb/testsuite/gdb.cp/print-demangle.exp   | 32 +++++++++++++++++++++++
 gdb/testsuite/gdb.guile/scm-symbol.exp    |  4 +--
 gdb/testsuite/gdb.python/py-symbol.exp    |  2 +-
 8 files changed, 79 insertions(+), 16 deletions(-)
 create mode 100644 gdb/testsuite/gdb.cp/print-demangle.exp

-- 
2.17.2

Comments

Tom de Vries April 24, 2020, 4:06 p.m. | #1
On 25-03-2020 21:07, Tom Tromey wrote:
> The DWARF reader has had some odd code since the "physname" patches landed.

> 

> In particular, these patches caused PR symtab/12707; namely, they made

> it so "set print demangle off" no longer works.

> 

> This patch attempts to fix the problem.  It arranges to store the

> linkage name on the symbol if it exists, and it changes the DWARF

> reader so that the demangled name is no longer (usually) stored in the

> symbol's "linkage name" field.

> 

> c-linkage-name.exp needed a tweak, because it started working

> correctly.  This conforms to what I think ought to happen, so this

> seems like an improvement here.

> 

> compile-object-load.c needed a small change to use

> symbol_matches_search_name rather than directly examining the linkage

> name.  Looking directly at the name does the wrong thing for C++.

> 

> There is still some name-related confusion in the DWARF reader:

> 

> * "physname" often refers to the logical name and not what I would

>   consider to be the "physical" name;

> 

> * dwarf2_full_name, dwarf2_name, and dwarf2_physname all exist and

>   return different strings -- but this seems like at least one name

>   too many.  For example, Fortran requires dwarf2_full_name, but other

>   languages do not.

> 

> * To my surprise, dwarf2_physname prefers the form emitted by the

>   demangler over the one that it computes.  This seems backward to me,

>   given that the partial symbol reader prefers the opposite, and it

>   seems to me that this choice may perform better as well.

> 

> I didn't attempt to clean up these things.  It would be good to do,

> but whenever I contemplate it I get caught up in dreams of truly

> rewriting the DWARF reader instead.

> 


Hi,

As you mentioned on IRC, there's a regression with
gdb.dwarf2/dw2-bad-mips-linkage-name.exp and target board
cc-with-debug-names. I tracked that down to this patch in the series.

Using readelf -w, I can read the .debug_names section, and see without
this patch:
...
[  6] #0002b60b f: <3> DW_TAG_subprogram DW_IDX_compile_unit=3
DW_IDX_GNU_internal=1
[  8] #0002b60c g: <3> DW_TAG_subprogram DW_IDX_compile_unit=3
DW_IDX_GNU_internal=1
...
and with this patch:
...
[  6] #0ef9dc4b _Z1fv: <3> DW_TAG_subprogram DW_IDX_compile_unit=3
DW_IDX_GNU_internal=1
[  8] #0002b60c g: <3> DW_TAG_subprogram DW_IDX_compile_unit=3
DW_IDX_GNU_internal=1
...

So we end up with the mangled name for f in the index.  That looks
significant, but I'm not sure yet if that is the reason why we're not
able to print the type of f.

Thanks,
- Tom

> gdb/ChangeLog

> 2020-03-25  Tom Tromey  <tom@tromey.com>

> 

> 	PR symtab/12707:

> 	* dwarf2/read.c (add_partial_symbol): Use the linkage name if it

> 	exists.

> 	(new_symbol): Likewise.

> 	* compile/compile-object-load.c (get_out_value_type): Use

> 	symbol_matches_search_name.

> 

> gdb/testsuite/ChangeLog

> 2020-03-25  Tom Tromey  <tom@tromey.com>

> 

> 	PR symtab/12707:

> 	* gdb.python/py-symbol.exp: Update expected results for

> 	linkage_name test.

> 	* gdb.cp/print-demangle.exp: New file.

> 	* gdb.base/c-linkage-name.exp: Fix test.

> 	* gdb.guile/scm-symbol.exp: Update expected results for

> 	linkage_name test.

> ---

>  gdb/ChangeLog                             |  9 +++++++

>  gdb/compile/compile-object-load.c         |  7 ++---

>  gdb/dwarf2/read.c                         | 29 ++++++++++++++------

>  gdb/testsuite/ChangeLog                   | 10 +++++++

>  gdb/testsuite/gdb.base/c-linkage-name.exp |  2 +-

>  gdb/testsuite/gdb.cp/print-demangle.exp   | 32 +++++++++++++++++++++++

>  gdb/testsuite/gdb.guile/scm-symbol.exp    |  4 +--

>  gdb/testsuite/gdb.python/py-symbol.exp    |  2 +-

>  8 files changed, 79 insertions(+), 16 deletions(-)

>  create mode 100644 gdb/testsuite/gdb.cp/print-demangle.exp

> 

> diff --git a/gdb/compile/compile-object-load.c b/gdb/compile/compile-object-load.c

> index 3fe95183e32..be4fa767142 100644

> --- a/gdb/compile/compile-object-load.c

> +++ b/gdb/compile/compile-object-load.c

> @@ -402,6 +402,9 @@ get_out_value_type (struct symbol *func_sym, struct objfile *objfile,

>    int nblocks = 0;

>    int block_loop = 0;

>  

> +  lookup_name_info func_matcher (GCC_FE_WRAPPER_FUNCTION,

> +				 symbol_name_match_type::SEARCH_NAME);

> +

>    bv = SYMTAB_BLOCKVECTOR (func_sym->owner.symtab);

>    nblocks = BLOCKVECTOR_NBLOCKS (bv);

>  

> @@ -433,9 +436,7 @@ get_out_value_type (struct symbol *func_sym, struct objfile *objfile,

>        if (function != NULL

>  	  && (BLOCK_SUPERBLOCK (function_block)

>  	      == BLOCKVECTOR_BLOCK (bv, STATIC_BLOCK))

> -	  && (strcmp_iw (function->linkage_name (),

> -			 GCC_FE_WRAPPER_FUNCTION)

> -	      == 0))

> +	  && symbol_matches_search_name (function, func_matcher))

>  	break;

>      }

>    if (block_loop == nblocks)

> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c

> index 2bc7b521f2e..1e824ca399d 100644

> --- a/gdb/dwarf2/read.c

> +++ b/gdb/dwarf2/read.c

> @@ -8370,7 +8370,14 @@ add_partial_symbol (struct partial_die_info *pdi, struct dwarf2_cu *cu)

>      {

>        if (built_actual_name != nullptr)

>  	actual_name = objfile->intern (actual_name);

> -      psymbol.ginfo.set_linkage_name (actual_name);

> +      if (pdi->linkage_name == nullptr || cu->language == language_ada)

> +	psymbol.ginfo.set_linkage_name (actual_name);

> +      else

> +	{

> +	  psymbol.ginfo.set_demangled_name (actual_name,

> +					    &objfile->objfile_obstack);

> +	  psymbol.ginfo.set_linkage_name (pdi->linkage_name);

> +	}

>        add_psymbol_to_list (psymbol, *where, objfile);

>      }

>  }

> @@ -20550,7 +20557,6 @@ new_symbol (struct die_info *die, struct type *type, struct dwarf2_cu *cu,

>    name = dwarf2_name (die, cu);

>    if (name)

>      {

> -      const char *linkagename;

>        int suppress_add = 0;

>  

>        if (space)

> @@ -20561,14 +20567,21 @@ new_symbol (struct die_info *die, struct type *type, struct dwarf2_cu *cu,

>  

>        /* Cache this symbol's name and the name's demangled form (if any).  */

>        sym->set_language (cu->language, &objfile->objfile_obstack);

> -      linkagename = dwarf2_physname (name, die, cu);

> -      sym->compute_and_set_names (linkagename, false, objfile->per_bfd);

> -

>        /* Fortran does not have mangling standard and the mangling does differ

>  	 between gfortran, iFort etc.  */

> -      if (cu->language == language_fortran

> -          && symbol_get_demangled_name (sym) == NULL)

> -	sym->set_demangled_name (dwarf2_full_name (name, die, cu), NULL);

> +      const char *physname

> +	= (cu->language == language_fortran

> +	   ? dwarf2_full_name (name, die, cu)

> +	   : dwarf2_physname (name, die, cu));

> +      const char *linkagename = dw2_linkage_name (die, cu);

> +

> +      if (linkagename == nullptr || cu->language == language_ada)

> +	sym->set_linkage_name (physname);

> +      else

> +	{

> +	  sym->set_demangled_name (physname, &objfile->objfile_obstack);

> +	  sym->set_linkage_name (linkagename);

> +	}

>  

>        /* Default assumptions.

>           Use the passed type or decode it from the die.  */

> diff --git a/gdb/testsuite/gdb.base/c-linkage-name.exp b/gdb/testsuite/gdb.base/c-linkage-name.exp

> index 4551c8dcac2..cf3e3780bb6 100644

> --- a/gdb/testsuite/gdb.base/c-linkage-name.exp

> +++ b/gdb/testsuite/gdb.base/c-linkage-name.exp

> @@ -48,7 +48,7 @@ verify_psymtab_expanded c-linkage-name-2.c no

>  # Try to print MUNDANE, but using its linkage name.

>  

>  gdb_test "print symada__cS" \

> -         "'symada__cS' has unknown type; cast it to its declared type" \

> +         " = {a = 100829103}" \

>           "print symada__cS before partial symtab expansion"

>  

>  # Force the symbols to be expanded for the unit that contains

> diff --git a/gdb/testsuite/gdb.cp/print-demangle.exp b/gdb/testsuite/gdb.cp/print-demangle.exp

> new file mode 100644

> index 00000000000..9e0f706febf

> --- /dev/null

> +++ b/gdb/testsuite/gdb.cp/print-demangle.exp

> @@ -0,0 +1,32 @@

> +# Copyright (C) 2013, 2020 Free Software Foundation, Inc.

> +

> +# This program is free software; you can redistribute it and/or modify

> +# it under the terms of the GNU General Public License as published by

> +# the Free Software Foundation; either version 3 of the License, or

> +# (at your option) any later version.

> +#

> +# This program is distributed in the hope that it will be useful,

> +# but WITHOUT ANY WARRANTY; without even the implied warranty of

> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

> +# GNU General Public License for more details.

> +#

> +# You should have received a copy of the GNU General Public License

> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.

> +

> +if { [skip_cplus_tests] } { continue }

> +

> +standard_testfile bool.cc

> +

> +if {[prepare_for_testing $testfile.exp $testfile $srcfile {debug c++}]} {

> +    return -1

> +}

> +

> +runto_main

> +

> +gdb_breakpoint "return_true"

> +

> +gdb_continue_to_breakpoint "return_true"

> +

> +gdb_test_no_output "set print demangle off"

> +

> +gdb_test "frame" " _Z11return_truev .*"

> diff --git a/gdb/testsuite/gdb.guile/scm-symbol.exp b/gdb/testsuite/gdb.guile/scm-symbol.exp

> index 4addc0d10d0..486fc8fcfdb 100644

> --- a/gdb/testsuite/gdb.guile/scm-symbol.exp

> +++ b/gdb/testsuite/gdb.guile/scm-symbol.exp

> @@ -169,10 +169,8 @@ gdb_test "guile (print (symbol-name cplusfunc))" \

>      "= SimpleClass::valueofi().*" "test method.name"

>  gdb_test "guile (print (symbol-print-name cplusfunc))" \

>      "= SimpleClass::valueofi().*" "test method.print_name"

> -# FIXME: GDB is broken here and we're verifying broken behaviour.

> -# (linkage-name should be the mangled name)

>  gdb_test "guile (print (symbol-linkage-name cplusfunc))" \

> -    "SimpleClass::valueofi().*" "test method.linkage_name"

> +    "_ZN11SimpleClass8valueofiEv.*" "test method.linkage_name"

>  gdb_test "guile (print (= (symbol-addr-class cplusfunc) SYMBOL_LOC_BLOCK))" "= #t"

>  

>  # Test is_valid when the objfile is unloaded.  This must be the last

> diff --git a/gdb/testsuite/gdb.python/py-symbol.exp b/gdb/testsuite/gdb.python/py-symbol.exp

> index c4bae9f07f2..caa7ddc8007 100644

> --- a/gdb/testsuite/gdb.python/py-symbol.exp

> +++ b/gdb/testsuite/gdb.python/py-symbol.exp

> @@ -211,7 +211,7 @@ gdb_test "python print (cplusfunc.is_function)" \

>  

>  gdb_test "python print (cplusfunc.name)" "SimpleClass::valueofi().*" "test method.name"

>  gdb_test "python print (cplusfunc.print_name)" "SimpleClass::valueofi().*" "test method.print_name"

> -gdb_test "python print (cplusfunc.linkage_name)" "SimpleClass::valueofi().*" "test method.linkage_name"

> +gdb_test "python print (cplusfunc.linkage_name)" "_ZN11SimpleClass8valueofiEv.*" "test method.linkage_name"

>  gdb_test "python print (cplusfunc.addr_class == gdb.SYMBOL_LOC_BLOCK)" "True" "test method.addr_class"

>  

>  # Test is_valid when the objfile is unloaded.  This must be the last

>
Tom de Vries April 24, 2020, 6:09 p.m. | #2
On 24-04-2020 18:06, Tom de Vries wrote:
> On 25-03-2020 21:07, Tom Tromey wrote:

>> The DWARF reader has had some odd code since the "physname" patches landed.

>>

>> In particular, these patches caused PR symtab/12707; namely, they made

>> it so "set print demangle off" no longer works.

>>

>> This patch attempts to fix the problem.  It arranges to store the

>> linkage name on the symbol if it exists, and it changes the DWARF

>> reader so that the demangled name is no longer (usually) stored in the

>> symbol's "linkage name" field.

>>

>> c-linkage-name.exp needed a tweak, because it started working

>> correctly.  This conforms to what I think ought to happen, so this

>> seems like an improvement here.

>>

>> compile-object-load.c needed a small change to use

>> symbol_matches_search_name rather than directly examining the linkage

>> name.  Looking directly at the name does the wrong thing for C++.

>>

>> There is still some name-related confusion in the DWARF reader:

>>

>> * "physname" often refers to the logical name and not what I would

>>   consider to be the "physical" name;

>>

>> * dwarf2_full_name, dwarf2_name, and dwarf2_physname all exist and

>>   return different strings -- but this seems like at least one name

>>   too many.  For example, Fortran requires dwarf2_full_name, but other

>>   languages do not.

>>

>> * To my surprise, dwarf2_physname prefers the form emitted by the

>>   demangler over the one that it computes.  This seems backward to me,

>>   given that the partial symbol reader prefers the opposite, and it

>>   seems to me that this choice may perform better as well.

>>

>> I didn't attempt to clean up these things.  It would be good to do,

>> but whenever I contemplate it I get caught up in dreams of truly

>> rewriting the DWARF reader instead.

>>

> 

> Hi,

> 

> As you mentioned on IRC, there's a regression with

> gdb.dwarf2/dw2-bad-mips-linkage-name.exp and target board

> cc-with-debug-names. I tracked that down to this patch in the series.

> 

> Using readelf -w, I can read the .debug_names section, and see without

> this patch:

> ...

> [  6] #0002b60b f: <3> DW_TAG_subprogram DW_IDX_compile_unit=3

> DW_IDX_GNU_internal=1

> [  8] #0002b60c g: <3> DW_TAG_subprogram DW_IDX_compile_unit=3

> DW_IDX_GNU_internal=1

> ...

> and with this patch:

> ...

> [  6] #0ef9dc4b _Z1fv: <3> DW_TAG_subprogram DW_IDX_compile_unit=3

> DW_IDX_GNU_internal=1

> [  8] #0002b60c g: <3> DW_TAG_subprogram DW_IDX_compile_unit=3

> DW_IDX_GNU_internal=1

> ...

> 

> So we end up with the mangled name for f in the index.  That looks

> significant, but I'm not sure yet if that is the reason why we're not

> able to print the type of f.

> 


Hmm, one thing that is odd about this test-case is that it constructs a
C language CU, which contains a subprogram with DW_AT_MIPS_linkage_name
attribute with a C++ mangled name.

If I update the testcase to use a c++ language CU, the test passes:
...
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name.exp
b/gdb/testsuite/gdb.dwarf2/dw2-bad-mips-lin
kage-name.exp
index d00308a5702..5f01c41aaa3 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name.exp
+++ b/gdb/testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name.exp
@@ -38,7 +38,7 @@ Dwarf::assemble $asm_file {

     cu {} {
        DW_TAG_compile_unit {
-                {DW_AT_language @DW_LANG_C}
+                {DW_AT_language @DW_LANG_C_plus_plus}
                 {DW_AT_name     dw2-bad-mips-linkage-name.c}
                 {DW_AT_comp_dir /tmp}

@@ -78,5 +78,5 @@ if { [prepare_for_testing "failed to prepare"
${testfile} \
 # much matter what we test here, so long as we do something to make
 # sure that the DWARF is read.

-gdb_test "ptype f" " = bool \\(\\)"
-gdb_test "ptype g" " = bool \\(\\)"
+gdb_test "ptype f" " = bool \\(void\\)"
+gdb_test "ptype g" " = bool \\(void\\)"
...

Thanks,
- Tom
Tom Tromey April 24, 2020, 8:50 p.m. | #3
>>>>> "Tom" == Tom de Vries <tdevries@suse.de> writes:


Tom> Hmm, one thing that is odd about this test-case is that it constructs a
Tom> C language CU, which contains a subprogram with DW_AT_MIPS_linkage_name
Tom> attribute with a C++ mangled name.

This sounds very familiar.  I feel like I patched this at some point but
now I don't know where that patch went.

Tom> If I update the testcase to use a c++ language CU, the test passes:

I think this is the correct thing to do.
The main point of the test is to ensure that the linkage name with the
wrong form doesn't cause a crash:

		{DW_AT_MIPS_linkage_name 42 DW_FORM_data1}

I suggest you check this in.

thanks,
Tom

Patch

diff --git a/gdb/compile/compile-object-load.c b/gdb/compile/compile-object-load.c
index 3fe95183e32..be4fa767142 100644
--- a/gdb/compile/compile-object-load.c
+++ b/gdb/compile/compile-object-load.c
@@ -402,6 +402,9 @@  get_out_value_type (struct symbol *func_sym, struct objfile *objfile,
   int nblocks = 0;
   int block_loop = 0;
 
+  lookup_name_info func_matcher (GCC_FE_WRAPPER_FUNCTION,
+				 symbol_name_match_type::SEARCH_NAME);
+
   bv = SYMTAB_BLOCKVECTOR (func_sym->owner.symtab);
   nblocks = BLOCKVECTOR_NBLOCKS (bv);
 
@@ -433,9 +436,7 @@  get_out_value_type (struct symbol *func_sym, struct objfile *objfile,
       if (function != NULL
 	  && (BLOCK_SUPERBLOCK (function_block)
 	      == BLOCKVECTOR_BLOCK (bv, STATIC_BLOCK))
-	  && (strcmp_iw (function->linkage_name (),
-			 GCC_FE_WRAPPER_FUNCTION)
-	      == 0))
+	  && symbol_matches_search_name (function, func_matcher))
 	break;
     }
   if (block_loop == nblocks)
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 2bc7b521f2e..1e824ca399d 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -8370,7 +8370,14 @@  add_partial_symbol (struct partial_die_info *pdi, struct dwarf2_cu *cu)
     {
       if (built_actual_name != nullptr)
 	actual_name = objfile->intern (actual_name);
-      psymbol.ginfo.set_linkage_name (actual_name);
+      if (pdi->linkage_name == nullptr || cu->language == language_ada)
+	psymbol.ginfo.set_linkage_name (actual_name);
+      else
+	{
+	  psymbol.ginfo.set_demangled_name (actual_name,
+					    &objfile->objfile_obstack);
+	  psymbol.ginfo.set_linkage_name (pdi->linkage_name);
+	}
       add_psymbol_to_list (psymbol, *where, objfile);
     }
 }
@@ -20550,7 +20557,6 @@  new_symbol (struct die_info *die, struct type *type, struct dwarf2_cu *cu,
   name = dwarf2_name (die, cu);
   if (name)
     {
-      const char *linkagename;
       int suppress_add = 0;
 
       if (space)
@@ -20561,14 +20567,21 @@  new_symbol (struct die_info *die, struct type *type, struct dwarf2_cu *cu,
 
       /* Cache this symbol's name and the name's demangled form (if any).  */
       sym->set_language (cu->language, &objfile->objfile_obstack);
-      linkagename = dwarf2_physname (name, die, cu);
-      sym->compute_and_set_names (linkagename, false, objfile->per_bfd);
-
       /* Fortran does not have mangling standard and the mangling does differ
 	 between gfortran, iFort etc.  */
-      if (cu->language == language_fortran
-          && symbol_get_demangled_name (sym) == NULL)
-	sym->set_demangled_name (dwarf2_full_name (name, die, cu), NULL);
+      const char *physname
+	= (cu->language == language_fortran
+	   ? dwarf2_full_name (name, die, cu)
+	   : dwarf2_physname (name, die, cu));
+      const char *linkagename = dw2_linkage_name (die, cu);
+
+      if (linkagename == nullptr || cu->language == language_ada)
+	sym->set_linkage_name (physname);
+      else
+	{
+	  sym->set_demangled_name (physname, &objfile->objfile_obstack);
+	  sym->set_linkage_name (linkagename);
+	}
 
       /* Default assumptions.
          Use the passed type or decode it from the die.  */
diff --git a/gdb/testsuite/gdb.base/c-linkage-name.exp b/gdb/testsuite/gdb.base/c-linkage-name.exp
index 4551c8dcac2..cf3e3780bb6 100644
--- a/gdb/testsuite/gdb.base/c-linkage-name.exp
+++ b/gdb/testsuite/gdb.base/c-linkage-name.exp
@@ -48,7 +48,7 @@  verify_psymtab_expanded c-linkage-name-2.c no
 # Try to print MUNDANE, but using its linkage name.
 
 gdb_test "print symada__cS" \
-         "'symada__cS' has unknown type; cast it to its declared type" \
+         " = {a = 100829103}" \
          "print symada__cS before partial symtab expansion"
 
 # Force the symbols to be expanded for the unit that contains
diff --git a/gdb/testsuite/gdb.cp/print-demangle.exp b/gdb/testsuite/gdb.cp/print-demangle.exp
new file mode 100644
index 00000000000..9e0f706febf
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/print-demangle.exp
@@ -0,0 +1,32 @@ 
+# Copyright (C) 2013, 2020 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+if { [skip_cplus_tests] } { continue }
+
+standard_testfile bool.cc
+
+if {[prepare_for_testing $testfile.exp $testfile $srcfile {debug c++}]} {
+    return -1
+}
+
+runto_main
+
+gdb_breakpoint "return_true"
+
+gdb_continue_to_breakpoint "return_true"
+
+gdb_test_no_output "set print demangle off"
+
+gdb_test "frame" " _Z11return_truev .*"
diff --git a/gdb/testsuite/gdb.guile/scm-symbol.exp b/gdb/testsuite/gdb.guile/scm-symbol.exp
index 4addc0d10d0..486fc8fcfdb 100644
--- a/gdb/testsuite/gdb.guile/scm-symbol.exp
+++ b/gdb/testsuite/gdb.guile/scm-symbol.exp
@@ -169,10 +169,8 @@  gdb_test "guile (print (symbol-name cplusfunc))" \
     "= SimpleClass::valueofi().*" "test method.name"
 gdb_test "guile (print (symbol-print-name cplusfunc))" \
     "= SimpleClass::valueofi().*" "test method.print_name"
-# FIXME: GDB is broken here and we're verifying broken behaviour.
-# (linkage-name should be the mangled name)
 gdb_test "guile (print (symbol-linkage-name cplusfunc))" \
-    "SimpleClass::valueofi().*" "test method.linkage_name"
+    "_ZN11SimpleClass8valueofiEv.*" "test method.linkage_name"
 gdb_test "guile (print (= (symbol-addr-class cplusfunc) SYMBOL_LOC_BLOCK))" "= #t"
 
 # Test is_valid when the objfile is unloaded.  This must be the last
diff --git a/gdb/testsuite/gdb.python/py-symbol.exp b/gdb/testsuite/gdb.python/py-symbol.exp
index c4bae9f07f2..caa7ddc8007 100644
--- a/gdb/testsuite/gdb.python/py-symbol.exp
+++ b/gdb/testsuite/gdb.python/py-symbol.exp
@@ -211,7 +211,7 @@  gdb_test "python print (cplusfunc.is_function)" \
 
 gdb_test "python print (cplusfunc.name)" "SimpleClass::valueofi().*" "test method.name"
 gdb_test "python print (cplusfunc.print_name)" "SimpleClass::valueofi().*" "test method.print_name"
-gdb_test "python print (cplusfunc.linkage_name)" "SimpleClass::valueofi().*" "test method.linkage_name"
+gdb_test "python print (cplusfunc.linkage_name)" "_ZN11SimpleClass8valueofiEv.*" "test method.linkage_name"
 gdb_test "python print (cplusfunc.addr_class == gdb.SYMBOL_LOC_BLOCK)" "True" "test method.addr_class"
 
 # Test is_valid when the objfile is unloaded.  This must be the last