[PATCH V2 1/1] Fix of default lookup for "this" symbol.

Walfred Tedeschi
2016-06-28T12:52:09Z

Using the default lookup for the symbol "this" might lead to segmentation
fault in GDB.
Some languages, e.g. Fortran, use as default lookup routine the C++
routines.
For those languages "this" can be the instance of a class or even the
definition of a class.
When an instance of a class having the name "this" is evaluated
in GDB a segmentation fault was observed.

As example of the issue take into consideration the Fortran code:
type foo
real :: a
type(bar) :: x
character*7 :: b
end type foo
type(foo) :: this

Issue appears when evaluating the variable "this" in GDB.

Within the language definition structure there is a field that represents
the name of the special symbol used for the C++ "this" for the language
being described.
The fix presented here takes into account the aforementioned field. In the
case the aforementioned field is NULL "this" is not represented in the
language described and the lookup should return a null_block_symbol.

Tests: Performed tests with gfortran and ifort.

Reviewed:
https://sourceware.org/ml/gdb-patches/2016-04/msg00068.html

After the commited patch:
https://sourceware.org/ml/gdb-patches/2016-06/msg00364.html
Patch can be applied.

2016-06-16 Walfred Tedeschi <walfred.tedeschi@intel.com>

gdb/ChangeLog:

* cp-namespace.c (cp_lookup_bare_symbol): Add check for the
name_of_this in order to return a null symbol when looking up
for "this".

gdb/testsuite/ChangeLog:

* gdb.fortran/derived-types.exp (result_line, result_line_2):
New variables.
(print this%a, print this%b, print this): New tests.
* gdb.fortran/derived-types.f90 (this): New object and
initialization.

---
gdb/cp-namespace.c | 5 ++++-
gdb/testsuite/gdb.fortran/derived-type.exp | 35 ++++++++++++++++++++++++++++--
gdb/testsuite/gdb.fortran/derived-type.f90 | 7 +++++-
3 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/gdb/cp-namespace.c b/gdb/cp-namespace.c
index 016a42f..f34e383 100644
--- a/gdb/cp-namespace.c
+++ b/gdb/cp-namespace.c
@@ -206,10 +206,13 @@ cp_lookup_bare_symbol (const struct language_defn *langdef,
struct block_symbol lang_this;
struct type *type;

- lang_this = lookup_language_this (language_def (language_cplus), block);
+ if (langdef != NULL)
+ lang_this = lookup_language_this (langdef, block);
+
if (lang_this.symbol == NULL)
return null_block_symbol;

+
type = check_typedef (TYPE_TARGET_TYPE (SYMBOL_TYPE (lang_this.symbol)));
/* If TYPE_NAME is NULL, abandon trying to find this symbol.
This can happen for lambda functions compiled with clang++,
diff --git a/gdb/testsuite/gdb.fortran/derived-type.exp b/gdb/testsuite/gdb.fortran/derived-type.exp
index 32431bc..2781850 100644
--- a/gdb/testsuite/gdb.fortran/derived-type.exp
+++ b/gdb/testsuite/gdb.fortran/derived-type.exp
@@ -73,14 +73,45 @@ gdb_test_multiple $test $test {
gdb_test "print q%x%c" "\\$\[0-9\]+ = 1"
gdb_test "print q%x%d" "\\$\[0-9\]+ = 2\\.375"

+set result_line "= \\( a = 3.125, x = \\( c = 1, d = 2\\.375 \\),\
+b = 'abcdefg' \\)\r\n$gdb_prompt $"
+
+# Used in case compiler generates an array of characters.
+set result_line_2 " = \\( a = 3.125, x = \\( 1, 2\\.375 \\),\
+b = \\('abcdefg'\\) \\)\r\n$gdb_prompt $"
+
set test "print q"
gdb_test_multiple $test $test {
- -re "\\$\[0-9\]+ = \\( a = 3.125, x = \\( c = 1, d = 2\\.375 \\), b = 'abcdefg' \\)\r\n$gdb_prompt $" {
+ -re $result_line {
pass $test
}
- -re "\\$\[0-9\]+ = \\( a = 3.125, x = \\( 1, 2\\.375 \\), b = \\('abcdefg'\\) \\)\r\n$gdb_prompt $" {
+ -re $result_line_2 {
# Compiler should produce string, not an array of characters.
setup_xfail "*-*-*"
fail $test
}
}
+
+gdb_test "print this%a" " = 3\\.125"
+
+set test "print this%b"
+gdb_test_multiple $test $test {
+ -re " = 'abcdefg'\r\n$gdb_prompt $" {
+ pass $test
+ }
+ -re $result_line_2 {
+ setup_xfail "*-*-*"
+ fail $test
+ }
+}
+
+set test "print this"
+gdb_test_multiple $test $test {
+ -re $result_line {
+ pass $test
+ }
+ -re $result_line_2 {
+ setup_xfail "*-*-*"
+ fail $test
+ }
+}
diff --git a/gdb/testsuite/gdb.fortran/derived-type.f90 b/gdb/testsuite/gdb.fortran/derived-type.f90
index 2cb2339..aad1553 100644
--- a/gdb/testsuite/gdb.fortran/derived-type.f90
+++ b/gdb/testsuite/gdb.fortran/derived-type.f90
@@ -29,12 +29,17 @@ program main
end type foo
type(foo) :: q
type(bar) :: p
+ type(foo) :: this

p = bar(1, 2.375)
q%a = 3.125
q%b = "abcdefg"
q%x%c = 1
q%x%d = 2.375
- print *,p,q
+ this%a = 3.125
+ this%b = "abcdefg"
+ this%x%c = 1
+ this%x%d = 2.375
+ print *,p,q,this

end program main
--
2.7.4