[PATCH 12/13] Fix calling prototyped functions via function pointers

Pedro Alves
2017-07-13T02:29:29Z

Calling a prototyped function via a function pointer with the right
prototype doesn't work correctly, if the called function requires
argument coercion... Like, e.g., with:

float mult (float f1, float f2) { return f1 * f2; }

(gdb) p mult (2, 3.5)
$1 = 7
(gdb) p ((float (*) (float, float)) mult) (2, 3.5)
$2 = 0

both calls should have returned the same, of course. The problem is
that GDB misses marking the type of the function pointer target as
prototyped...

Without the fix, the new test fails like this:

(gdb) p ((int (*) (float, float)) t_float_values2)(3.14159,float_val2)
$30 = 0
(gdb) FAIL: gdb.base/callfuncs.exp: p ((int (*) (float, float)) t_float_values2)(3.14159,float_val2)

gdb/ChangeLog:
yyyy-mm-dd Pedro Alves <palves@redhat.com>

* gdbtypes.c (lookup_function_type_with_arguments): Mark function
types with more than one parameter as prototyped.

gdb/ChangeLog:
yyyy-mm-dd Pedro Alves <palves@redhat.com>

* gdb.base/callfuncs.exp (do_function_calls): New parameter
"prototypes". Test calling float functions via prototyped and
unprototyped function pointers.
(perform_all_tests): New parameter "prototypes". Pass it down.
(top level): Pass down "prototypes" parameter to
perform_all_tests.
---
gdb/gdbtypes.c | 2 ++
gdb/testsuite/gdb.base/callfuncs.exp | 26 +++++++++++++++++++++-----
2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c
index 674a724..fc86225 100644
--- a/gdb/gdbtypes.c
+++ b/gdb/gdbtypes.c
@@ -547,6 +547,8 @@ lookup_function_type_with_arguments (struct type *type,
gdb_assert (nparams == 0);
TYPE_PROTOTYPED (fn) = 1;
}
+ else
+ TYPE_PROTOTYPED (fn) = 1;
}

TYPE_NFIELDS (fn) = nparams;
diff --git a/gdb/testsuite/gdb.base/callfuncs.exp b/gdb/testsuite/gdb.base/callfuncs.exp
index 3651963..a537ebd 100644
--- a/gdb/testsuite/gdb.base/callfuncs.exp
+++ b/gdb/testsuite/gdb.base/callfuncs.exp
@@ -39,7 +39,7 @@ set skip_float_test [gdb_skip_float_test]
# specifies that the numeric value of a relational or logical expression
# (computed in the inferior) is 1 for true and 0 for false.

-proc do_function_calls {} {
+proc do_function_calls {prototypes} {
global gdb_prompt skip_float_test

# We need to up this because this can be really slow on some boards.
@@ -95,11 +95,25 @@ proc do_function_calls {} {
setup_xfail "mn10300-*-*"
if { [test_compiler_info "armcc-*"] } { setup_xfail "*-*-*" }
gdb_test "p t_float_values(float_val1,-2.3765)" " = 1"
+ # Same, via unprototyped function pointer (t_float_values is
+ # always unprototyped).
+ gdb_test "p ((int (*) ()) t_float_values)(float_val1,-2.3765)" " = 1"

# Test passing of arguments which might not be widened.
gdb_test "p t_float_values2(0.0,0.0)" " = 0"
+ # Same, via function pointer.
+ if {$prototypes} {
+ gdb_test "p ((int (*) (float, float)) t_float_values2)(0.0,0.0)" " = 0"
+ } else {
+ gdb_test "p ((int (*) ()) t_float_values2)(0.0,0.0)" " = 0"
+ }

gdb_test "p t_float_values2(3.14159,float_val2)" " = 1"
+ if {$prototypes} {
+ gdb_test "p ((int (*) (float, float)) t_float_values2)(3.14159,float_val2)" " = 1"
+ } else {
+ gdb_test "p ((int (*) ()) t_float_values2)(3.14159,float_val2)" " = 1"
+ }

gdb_test "p t_float_many_args (float_val1, float_val2, float_val3, float_val4, float_val5, float_val6, float_val7, float_val8, float_val9, float_val10, float_val11, float_val12, float_val13, float_val14, float_val15)" " = 1" "call function with many float arguments."

@@ -315,7 +329,7 @@ proc rerun_and_prepare {} {
"next to t_structs_c"
}

-proc perform_all_tests {} {
+proc perform_all_tests {prototypes} {
gdb_test_no_output "set print sevenbit-strings"
gdb_test_no_output "set print address off"
gdb_test_no_output "set width 0"
@@ -326,7 +340,7 @@ proc perform_all_tests {} {
set old_reg_content [fetch_all_registers "retrieve original register contents"]

# Perform function calls.
- do_function_calls
+ do_function_calls $prototypes

# Check if all registers still have the same value.
set new_reg_content [fetch_all_registers \
@@ -500,9 +514,11 @@ proc perform_all_tests {} {
# Perform all tests with and without function prototypes.

if { ![prepare_for_testing "failed to prepare" $testfile $srcfile "$compile_flags additional_flags=-DPROTOTYPES"] } {
- perform_all_tests
+ perform_all_tests 1
}

if { ![prepare_for_testing "failed to prepare" $testfile $srcfile "$compile_flags additional_flags=-DNO_PROTOTYPES"] } {
- with_test_prefix "noproto" perform_all_tests
+ with_test_prefix "noproto" {
+ perform_all_tests 0
+ }
}
--
2.5.5