Re: [PATCH] Fix windows-nat.c for -Wnarrowing

Tom Tromey
2018-08-29T19:31:32Z

>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

Pedro> If you're going to fix it, I'd go with my earlier suggestion:

Pedro> It'd be easily fixable by removing that terminator
Pedro> entry and using range-for in the other #if 0 block.

Ok, I know you said not to bother, but ...
Here's what I plan to checkin.

Tom

commit dbf105c6d25c16dee30af67f70bc468afffe6249
Author: Tom Tromey <tom@tromey.com>
Date: Wed Aug 29 11:37:42 2018 -0600

Fix windows-nat.c for -Wnarrowing

Sergio pointed out that the Windows builder was failing due to the
-Wnarrowing patch, with:

../../binutils-gdb/gdb/windows-nat.c:301:27: error: narrowing conversion of '3221225477' from 'DWORD {aka long unsigned int}' to 'int' inside { } [-Wnarrowing]
{-1, GDB_SIGNAL_UNKNOWN}};
^
../../binutils-gdb/gdb/windows-nat.c:301:27: error: narrowing conversion of '3221225725' from 'DWORD {aka long unsigned int}' to 'int' inside { } [-Wnarrowing]
../../binutils-gdb/gdb/windows-nat.c:301:27: error: narrowing conversion of '2147483651' from 'DWORD {aka long unsigned int}' to 'int' inside { } [-Wnarrowing]
../../binutils-gdb/gdb/windows-nat.c:301:27: error: narrowing conversion of '2147483652' from 'DWORD {aka long unsigned int}' to 'int' inside { } [-Wnarrowing]
../../binutils-gdb/gdb/windows-nat.c:301:27: error: narrowing conversion of '3221225614' from 'DWORD {aka long unsigned int}' to 'int' inside { } [-Wnarrowing]

Looking into this, I found two things.

First, in struct xlate_exception, it is better to have "them" be of
type DWORD, as that's the type actually in use.

Second, struct xlate_exception and xlate are not used in this file,
because the code in windows_nat_target::resume is #if'd out.

This patch changes the type of "them", but also similarly #if's out
this object.

In order to avoid a narrowing warning from the -1 entry, at Pedro's
suggestion I have removed this and changed windows_nat_target::resume
to use ranged for.

Tested by rebuilding using the mingw toolchain on x86-64 Fedora 28. I
also tested it by temporarily removing the "#if 0"s and rebuilding.

gdb/ChangeLog
2018-08-29 Tom Tromey <tom@tromey.com>

* windows-nat.c (struct xlate_exception) <them>: Change type to
DWORD.
(xlate): Fix formatting. Remove last entry.
(struct xlate_exception, xlate): Comment out.
(windows_nat_target::resume): Use ranged for.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index a30dacee4a3..f7e8922cdcd 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,11 @@
+2018-08-29 Tom Tromey <tom@tromey.com>
+
+ * windows-nat.c (struct xlate_exception) <them>: Change type to
+ DWORD.
+ (xlate): Fix formatting. Remove last entry.
+ (struct xlate_exception, xlate): Comment out.
+ (windows_nat_target::resume): Use ranged for.
+
2018-08-29 Sergio Durigan Junior <sergiodj@redhat.com>

PR gdb/23555
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index aea502638e0..da663496e5a 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -280,26 +280,29 @@ static const int *mappings;
a segment register or not. */
static segment_register_p_ftype *segment_register_p;

+/* See windows_nat_target::resume to understand why this is commented
+ out. */
+#if 0
/* This vector maps the target's idea of an exception (extracted
from the DEBUG_EVENT structure) to GDB's idea. */

struct xlate_exception
{
- int them;
+ DWORD them;
enum gdb_signal us;
};

-static const struct xlate_exception
- xlate[] =
+static const struct xlate_exception xlate[] =
{
{EXCEPTION_ACCESS_VIOLATION, GDB_SIGNAL_SEGV},
{STATUS_STACK_OVERFLOW, GDB_SIGNAL_SEGV},
{EXCEPTION_BREAKPOINT, GDB_SIGNAL_TRAP},
{DBG_CONTROL_C, GDB_SIGNAL_INT},
{EXCEPTION_SINGLE_STEP, GDB_SIGNAL_TRAP},
- {STATUS_FLOAT_DIVIDE_BY_ZERO, GDB_SIGNAL_FPE},
- {-1, GDB_SIGNAL_UNKNOWN}};
+ {STATUS_FLOAT_DIVIDE_BY_ZERO, GDB_SIGNAL_FPE}
+};

+#endif /* 0 */

struct windows_nat_target final : public x86_nat_target<inf_child_target>
{
@@ -1408,12 +1411,11 @@ windows_nat_target::resume (ptid_t ptid, int step, enum gdb_signal sig)
structure when passing the exception to the inferior.
Note that this seems possible in the exception handler itself. */
{
- int i;
- for (i = 0; xlate[i].them != -1; i++)
- if (xlate[i].us == sig)
+ for (const xlate_exception &x : xlate)
+ if (x.us == sig)
{
current_event.u.Exception.ExceptionRecord.ExceptionCode
- = xlate[i].them;
+ = x.them;
continue_status = DBG_EXCEPTION_NOT_HANDLED;
break;
}