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gtypes: Define signed integer minimum values in terms of maximum values

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This is what limits.h does. It avoids a problem when compiling with MSVC
(in C++ mode) on Windows, whereby the 0x80000000 constant is interpreted
as unsigned, and *then* the unary minus is applied to it.

https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-2-c4146?view=vs-2017

Add a test which should hopefully catch problems with different
compilers’ interpretations of this in future.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://gitlab.gnome.org/GNOME/glib/issues/1663
This commit is contained in:
Philip Withnall 2019-01-23 13:07:44 +00:00
parent 7035462da0
commit 6a2cfde29f
2 changed files with 35 additions and 4 deletions
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8
glib/gtypes.h
View File

@ -58,19 +58,19 @@ typedef float gfloat;
typedef double gdouble;
/* Define min and max constants for the fixed size numerical types */
#define G_MININT8 ((gint8) -0x80)
#define G_MININT8 ((gint8) (-G_MAXINT8 - 1))
#define G_MAXINT8 ((gint8) 0x7f)
#define G_MAXUINT8 ((guint8) 0xff)
#define G_MININT16 ((gint16) -0x8000)
#define G_MININT16 ((gint16) (-G_MAXINT16 - 1))
#define G_MAXINT16 ((gint16) 0x7fff)
#define G_MAXUINT16 ((guint16) 0xffff)
#define G_MININT32 ((gint32) -0x80000000)
#define G_MININT32 ((gint32) (-G_MAXINT32 - 1))
#define G_MAXINT32 ((gint32) 0x7fffffff)
#define G_MAXUINT32 ((guint32) 0xffffffff)
#define G_MININT64 ((gint64) G_GINT64_CONSTANT(-0x8000000000000000))
#define G_MININT64 ((gint64) (-G_MAXINT64 - G_GINT64_CONSTANT(1)))
#define G_MAXINT64 G_GINT64_CONSTANT(0x7fffffffffffffff)
#define G_MAXUINT64 G_GUINT64_CONSTANT(0xffffffffffffffff)

31
glib/tests/utils.c
View File

@ -655,6 +655,36 @@ test_check_setuid (void)
g_assert (!res);
}
/* Test the defined integer limits are correct, as some compilers have had
* problems with signed/unsigned conversion in the past. These limits should not
* vary between platforms, compilers or architectures.
*
* Use string comparisons to avoid the same systematic problems with unary minus
* application in C++. See https://gitlab.gnome.org/GNOME/glib/issues/1663. */
static void
test_int_limits (void)
{
gchar *str = NULL;
g_test_bug ("https://gitlab.gnome.org/GNOME/glib/issues/1663");
str = g_strdup_printf ("%d %d %u\n"
"%" G_GINT16_FORMAT " %" G_GINT16_FORMAT " %" G_GUINT16_FORMAT "\n"
"%" G_GINT32_FORMAT " %" G_GINT32_FORMAT " %" G_GUINT32_FORMAT "\n"
"%" G_GINT64_FORMAT " %" G_GINT64_FORMAT " %" G_GUINT64_FORMAT "\n",
G_MININT8, G_MAXINT8, G_MAXUINT8,
G_MININT16, G_MAXINT16, G_MAXUINT16,
G_MININT32, G_MAXINT32, G_MAXUINT32,
G_MININT64, G_MAXINT64, G_MAXUINT64);
g_assert_cmpstr (str, ==,
"-128 127 255\n"
"-32768 32767 65535\n"
"-2147483648 2147483647 4294967295\n"
"-9223372036854775808 9223372036854775807 18446744073709551615\n");
g_free (str);
}
int
main (int argc,
char *argv[])
@ -706,6 +736,7 @@ main (int argc,
g_test_add_func ("/utils/nullify", test_nullify);
g_test_add_func ("/utils/atexit", test_atexit);
g_test_add_func ("/utils/check-setuid", test_check_setuid);
g_test_add_func ("/utils/int-limits", test_int_limits);
return g_test_run ();
}