[PATCH] Fix crash in Fortran code

[PATCH] Fix crash in Fortran code

[Tom Tromey]

PR fortran/28801 points out a gdb crash that can be provoked by
certain Fortran code.  The bug is that f77_get_upperbound assumes the
property is either a constant or undefined, but in this case it is
PROP_LOCEXPR.

This patch fixes the crash by making this function (and the
lower-bound one as well) do the correct check before calling
'const_val'.

Thanks to Andrew for writing the test case.

Co-authored-by: Andrew Burgess <aburgess@redhat.com>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28801
---
 gdb/f-valprint.c                              |   4 +-
 gdb/testsuite/gdb.dwarf2/fortran-var-string.c |  31 ++++
 .../gdb.dwarf2/fortran-var-string.exp         | 175 ++++++++++++++++++
 3 files changed, 208 insertions(+), 2 deletions(-)
 create mode 100644 gdb/testsuite/gdb.dwarf2/fortran-var-string.c
 create mode 100644 gdb/testsuite/gdb.dwarf2/fortran-var-string.exp

diff --git a/gdb/f-valprint.c b/gdb/f-valprint.c
index 6a199f17c1e..b64750bac7b 100644
--- a/gdb/f-valprint.c
+++ b/gdb/f-valprint.c
@@ -43,7 +43,7 @@ static void f77_get_dynamic_length_of_aggregate (struct type *);
 LONGEST
 f77_get_lowerbound (struct type *type)
 {
-  if (type->bounds ()->low.kind () == PROP_UNDEFINED)
+  if (type->bounds ()->low.kind () != PROP_CONST)
     error (_("Lower bound may not be '*' in F77"));
 
   return type->bounds ()->low.const_val ();
@@ -52,7 +52,7 @@ f77_get_lowerbound (struct type *type)
 LONGEST
 f77_get_upperbound (struct type *type)
 {
-  if (type->bounds ()->high.kind () == PROP_UNDEFINED)
+  if (type->bounds ()->high.kind () != PROP_CONST)
     {
       /* We have an assumed size array on our hands.  Assume that
 	 upper_bound == lower_bound so that we show at least 1 element.
diff --git a/gdb/testsuite/gdb.dwarf2/fortran-var-string.c b/gdb/testsuite/gdb.dwarf2/fortran-var-string.c
new file mode 100644
index 00000000000..a677b7e6550
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/fortran-var-string.c
@@ -0,0 +1,31 @@
+/* Copyright 2022 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/>.  */
+
+/* In the generated DWARF, we'll pretend that ARG is a string with dynamic
+   length.  */
+int
+main_helper (void *arg)
+{
+  asm ("main_helper_label: .globl main_helper_label");
+  return 0;
+}
+
+int
+main (void)
+{
+  asm ("main_label: .globl main_label");
+  main_helper (0);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.dwarf2/fortran-var-string.exp b/gdb/testsuite/gdb.dwarf2/fortran-var-string.exp
new file mode 100644
index 00000000000..793c4418fd6
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/fortran-var-string.exp
@@ -0,0 +1,175 @@
+# Copyright 2022 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/>.
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+standard_testfile .c -dw.S
+
+# We need to know the size of integer and address types in order
+# to write some of the debugging info we'd like to generate.
+#
+# For that, we ask GDB by debugging our dynarr-ptr.c program.
+# Any program would do, but since we already have dynarr-ptr.c
+# specifically for this testcase, might as well use that.
+
+if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
+    return -1
+}
+
+# Make some DWARF for the test.
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    set int_size [get_sizeof "int" 4]
+
+    get_func_info main
+    get_func_info main_helper
+
+    cu {} {
+	DW_TAG_compile_unit {
+                {DW_AT_language @DW_LANG_Fortran90}
+                {DW_AT_name     fortran-var-string.f90}
+                {DW_AT_comp_dir /tmp}
+        } {
+	    declare_labels integer_label string_label array_lb_label \
+		array_ub_label
+
+	    DW_TAG_subprogram {
+		{name main}
+		{low_pc $main_helper_start addr}
+		{high_pc $main_helper_len data8}
+		{DW_AT_type :$integer_label}
+		{DW_AT_decl_file 1 data1}
+		{DW_AT_decl_line 1 data1}
+	    }
+
+	    DW_TAG_subprogram {
+		{name test_1_func}
+		{low_pc $main_start addr}
+		{high_pc $main_len data8}
+		{DW_AT_type :$integer_label}
+		{DW_AT_decl_file 1 data1}
+		{DW_AT_decl_line 2 data1}
+	    } {
+		formal_parameter {
+		    {name arg1}
+		    {type :$string_label}
+		}
+	    }
+
+	    DW_TAG_subprogram {
+		{name test_2_func}
+		{low_pc $main_start addr}
+		{high_pc $main_len data8}
+		{DW_AT_type :$integer_label}
+		{DW_AT_decl_file 1 data1}
+		{DW_AT_decl_line 3 data1}
+	    } {
+		formal_parameter {
+		    {name arg1}
+		    {type :$array_ub_label}
+		}
+	    }
+
+	    DW_TAG_subprogram {
+		{name test_3_func}
+		{low_pc $main_start addr}
+		{high_pc $main_len data8}
+		{DW_AT_type :$integer_label}
+		{DW_AT_decl_file 1 data1}
+		{DW_AT_decl_line 4 data1}
+	    } {
+		formal_parameter {
+		    {name arg1}
+		    {type :$array_lb_label}
+		}
+	    }
+
+	    integer_label: DW_TAG_base_type {
+		{DW_AT_byte_size $int_size DW_FORM_sdata}
+		{DW_AT_encoding  @DW_ATE_signed}
+		{DW_AT_name      integer}
+	    }
+
+	    string_label: DW_TAG_string_type {
+		{DW_AT_byte_size $int_size DW_FORM_sdata}
+		{DW_AT_name      .str.arg}
+		{DW_AT_string_length {} DW_FORM_block1}
+	    }
+
+	    array_lb_label: DW_TAG_array_type {
+		{DW_AT_ordering 1 data1}
+		{DW_AT_type :$integer_label}
+	    } {
+		DW_TAG_subrange_type {
+		    {DW_AT_lower_bound {} DW_FORM_block1}
+		    {DW_AT_upper_bound 10 DW_FORM_data1}
+		}
+	    }
+
+	    array_ub_label: DW_TAG_array_type {
+		{DW_AT_ordering 1 data1}
+		{DW_AT_type :$integer_label}
+	    } {
+		DW_TAG_subrange_type {
+		    {DW_AT_upper_bound {} DW_FORM_block1}
+		}
+	    }
+	}
+    }
+}
+
+# Now that we've generated the DWARF debugging info, rebuild our
+# program using our debug info instead of the info generated by
+# the compiler.
+
+if { [prepare_for_testing "failed to prepare" ${testfile} \
+	  [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_test_no_output "set language fortran"
+
+gdb_test "info functions test_1_func" \
+    "2:\\s+integer test_1_func\\(character\\*\\(\\*\\)\\);"
+
+# We print `1` here as the bound because GDB treats this as an assumed
+# size array, and just reports the lower bound value for the upper
+# bound.
+#
+# We might, in the future, decide that there's a better way we could
+# tell the user about the type of this array argument, when that
+# happens it's OK to change the expected results here.
+gdb_test "info functions test_2_func" \
+    "3:\\s+integer test_2_func\\(integer \\(1\\)\\);"
+
+# It's not completely clear that this error is correct here.  Why
+# can't the lower bound be a dynamic expression?
+#
+# This test was initially added to guard against the case where GDB
+# was crashing if/when it saw this situation.
+#
+# If later on, GDB's handling of array types with a dynamic loewr
+# bound changes, then it is possible that the expected result here
+# should change.
+gdb_test "info functions test_3_func" \
+    "4:\\s+Lower bound may not be '\\*' in F77"
-- 
2.31.1

Re: [PATCH] Fix crash in Fortran code

[Andrew Burgess]

Tom Tromey <tom@tromey.com> writes:

> PR fortran/28801 points out a gdb crash that can be provoked by
> certain Fortran code.  The bug is that f77_get_upperbound assumes the
> property is either a constant or undefined, but in this case it is
> PROP_LOCEXPR.
>
> This patch fixes the crash by making this function (and the
> lower-bound one as well) do the correct check before calling
> 'const_val'.

LGTM.  Great test case!

> Thanks to Andrew for writing the test case.

Thanks,
Andrew

>
> Co-authored-by: Andrew Burgess <aburgess@redhat.com>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28801
> ---
>  gdb/f-valprint.c                              |   4 +-
>  gdb/testsuite/gdb.dwarf2/fortran-var-string.c |  31 ++++
>  .../gdb.dwarf2/fortran-var-string.exp         | 175 ++++++++++++++++++
>  3 files changed, 208 insertions(+), 2 deletions(-)
>  create mode 100644 gdb/testsuite/gdb.dwarf2/fortran-var-string.c
>  create mode 100644 gdb/testsuite/gdb.dwarf2/fortran-var-string.exp
>
> diff --git a/gdb/f-valprint.c b/gdb/f-valprint.c
> index 6a199f17c1e..b64750bac7b 100644
> --- a/gdb/f-valprint.c
> +++ b/gdb/f-valprint.c
> @@ -43,7 +43,7 @@ static void f77_get_dynamic_length_of_aggregate (struct type *);
>  LONGEST
>  f77_get_lowerbound (struct type *type)
>  {
> -  if (type->bounds ()->low.kind () == PROP_UNDEFINED)
> +  if (type->bounds ()->low.kind () != PROP_CONST)
>      error (_("Lower bound may not be '*' in F77"));
>  
>    return type->bounds ()->low.const_val ();
> @@ -52,7 +52,7 @@ f77_get_lowerbound (struct type *type)
>  LONGEST
>  f77_get_upperbound (struct type *type)
>  {
> -  if (type->bounds ()->high.kind () == PROP_UNDEFINED)
> +  if (type->bounds ()->high.kind () != PROP_CONST)
>      {
>        /* We have an assumed size array on our hands.  Assume that
>  	 upper_bound == lower_bound so that we show at least 1 element.
> diff --git a/gdb/testsuite/gdb.dwarf2/fortran-var-string.c b/gdb/testsuite/gdb.dwarf2/fortran-var-string.c
> new file mode 100644
> index 00000000000..a677b7e6550
> --- /dev/null
> +++ b/gdb/testsuite/gdb.dwarf2/fortran-var-string.c
> @@ -0,0 +1,31 @@
> +/* Copyright 2022 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/>.  */
> +
> +/* In the generated DWARF, we'll pretend that ARG is a string with dynamic
> +   length.  */
> +int
> +main_helper (void *arg)
> +{
> +  asm ("main_helper_label: .globl main_helper_label");
> +  return 0;
> +}
> +
> +int
> +main (void)
> +{
> +  asm ("main_label: .globl main_label");
> +  main_helper (0);
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.dwarf2/fortran-var-string.exp b/gdb/testsuite/gdb.dwarf2/fortran-var-string.exp
> new file mode 100644
> index 00000000000..793c4418fd6
> --- /dev/null
> +++ b/gdb/testsuite/gdb.dwarf2/fortran-var-string.exp
> @@ -0,0 +1,175 @@
> +# Copyright 2022 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/>.
> +load_lib dwarf.exp
> +
> +# This test can only be run on targets which support DWARF-2 and use gas.
> +if {![dwarf2_support]} {
> +    return 0
> +}
> +
> +standard_testfile .c -dw.S
> +
> +# We need to know the size of integer and address types in order
> +# to write some of the debugging info we'd like to generate.
> +#
> +# For that, we ask GDB by debugging our dynarr-ptr.c program.
> +# Any program would do, but since we already have dynarr-ptr.c
> +# specifically for this testcase, might as well use that.
> +
> +if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
> +    return -1
> +}
> +
> +# Make some DWARF for the test.
> +set asm_file [standard_output_file $srcfile2]
> +Dwarf::assemble $asm_file {
> +    set int_size [get_sizeof "int" 4]
> +
> +    get_func_info main
> +    get_func_info main_helper
> +
> +    cu {} {
> +	DW_TAG_compile_unit {
> +                {DW_AT_language @DW_LANG_Fortran90}
> +                {DW_AT_name     fortran-var-string.f90}
> +                {DW_AT_comp_dir /tmp}
> +        } {
> +	    declare_labels integer_label string_label array_lb_label \
> +		array_ub_label
> +
> +	    DW_TAG_subprogram {
> +		{name main}
> +		{low_pc $main_helper_start addr}
> +		{high_pc $main_helper_len data8}
> +		{DW_AT_type :$integer_label}
> +		{DW_AT_decl_file 1 data1}
> +		{DW_AT_decl_line 1 data1}
> +	    }
> +
> +	    DW_TAG_subprogram {
> +		{name test_1_func}
> +		{low_pc $main_start addr}
> +		{high_pc $main_len data8}
> +		{DW_AT_type :$integer_label}
> +		{DW_AT_decl_file 1 data1}
> +		{DW_AT_decl_line 2 data1}
> +	    } {
> +		formal_parameter {
> +		    {name arg1}
> +		    {type :$string_label}
> +		}
> +	    }
> +
> +	    DW_TAG_subprogram {
> +		{name test_2_func}
> +		{low_pc $main_start addr}
> +		{high_pc $main_len data8}
> +		{DW_AT_type :$integer_label}
> +		{DW_AT_decl_file 1 data1}
> +		{DW_AT_decl_line 3 data1}
> +	    } {
> +		formal_parameter {
> +		    {name arg1}
> +		    {type :$array_ub_label}
> +		}
> +	    }
> +
> +	    DW_TAG_subprogram {
> +		{name test_3_func}
> +		{low_pc $main_start addr}
> +		{high_pc $main_len data8}
> +		{DW_AT_type :$integer_label}
> +		{DW_AT_decl_file 1 data1}
> +		{DW_AT_decl_line 4 data1}
> +	    } {
> +		formal_parameter {
> +		    {name arg1}
> +		    {type :$array_lb_label}
> +		}
> +	    }
> +
> +	    integer_label: DW_TAG_base_type {
> +		{DW_AT_byte_size $int_size DW_FORM_sdata}
> +		{DW_AT_encoding  @DW_ATE_signed}
> +		{DW_AT_name      integer}
> +	    }
> +
> +	    string_label: DW_TAG_string_type {
> +		{DW_AT_byte_size $int_size DW_FORM_sdata}
> +		{DW_AT_name      .str.arg}
> +		{DW_AT_string_length {} DW_FORM_block1}
> +	    }
> +
> +	    array_lb_label: DW_TAG_array_type {
> +		{DW_AT_ordering 1 data1}
> +		{DW_AT_type :$integer_label}
> +	    } {
> +		DW_TAG_subrange_type {
> +		    {DW_AT_lower_bound {} DW_FORM_block1}
> +		    {DW_AT_upper_bound 10 DW_FORM_data1}
> +		}
> +	    }
> +
> +	    array_ub_label: DW_TAG_array_type {
> +		{DW_AT_ordering 1 data1}
> +		{DW_AT_type :$integer_label}
> +	    } {
> +		DW_TAG_subrange_type {
> +		    {DW_AT_upper_bound {} DW_FORM_block1}
> +		}
> +	    }
> +	}
> +    }
> +}
> +
> +# Now that we've generated the DWARF debugging info, rebuild our
> +# program using our debug info instead of the info generated by
> +# the compiler.
> +
> +if { [prepare_for_testing "failed to prepare" ${testfile} \
> +	  [list $srcfile $asm_file] {nodebug}] } {
> +    return -1
> +}
> +
> +if ![runto_main] {
> +    return -1
> +}
> +
> +gdb_test_no_output "set language fortran"
> +
> +gdb_test "info functions test_1_func" \
> +    "2:\\s+integer test_1_func\\(character\\*\\(\\*\\)\\);"
> +
> +# We print `1` here as the bound because GDB treats this as an assumed
> +# size array, and just reports the lower bound value for the upper
> +# bound.
> +#
> +# We might, in the future, decide that there's a better way we could
> +# tell the user about the type of this array argument, when that
> +# happens it's OK to change the expected results here.
> +gdb_test "info functions test_2_func" \
> +    "3:\\s+integer test_2_func\\(integer \\(1\\)\\);"
> +
> +# It's not completely clear that this error is correct here.  Why
> +# can't the lower bound be a dynamic expression?
> +#
> +# This test was initially added to guard against the case where GDB
> +# was crashing if/when it saw this situation.
> +#
> +# If later on, GDB's handling of array types with a dynamic loewr
> +# bound changes, then it is possible that the expected result here
> +# should change.
> +gdb_test "info functions test_3_func" \
> +    "4:\\s+Lower bound may not be '\\*' in F77"
> -- 
> 2.31.1