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Re: [PATCH] add more detail to -Wconversion and -Woverflow (PR 80731)

On 05/29/2017 08:02 AM, Christophe Lyon wrote:

On 25 May 2017 at 00:16, Martin Sebor <msebor@gmail.com> wrote:

On 05/24/2017 11:08 AM, Joseph Myers wrote:


On Wed, 17 May 2017, Martin Sebor wrote:


@@ -1036,31 +1079,76 @@ warnings_for_convert_and_check (location_t loc,
tree type, tree expr,
          /* This detects cases like converting -129 or 256 to
             unsigned char.  */
          if (!int_fits_type_p (expr, c_common_signed_type (type)))
-           warning_at (loc, OPT_Woverflow,
-                       "large integer implicitly truncated to unsigned
type");
+           {
+             if (cst)
+               warning_at (loc, OPT_Woverflow,
+                           (TYPE_UNSIGNED (exprtype)
+                            ? "conversion from %qT to %qT "
+                            "changes value from %qE to %qE"
+                            : "unsigned conversion from %qT to %qT "
+                            "changes value from %qE to %qE"),
+                           exprtype, type, expr, result);
+             else
+               warning_at (loc, OPT_Woverflow,
+                           (TYPE_UNSIGNED (exprtype)
+                            ? "conversion from %qT to %qT "
+                            "changes the value of %qE"
+                            : "unsigned conversion from %qT to %qT "
+                            "changes the value of %qE"),
+                           exprtype, type, expr);
+           }



You need to use G_() around both arguments to ?:, otherwise only one will
get extracted for translation.


diff --git a/gcc/testsuite/c-c++-common/pr68657-1.c
b/gcc/testsuite/c-c++-common/pr68657-1.c
index 84f3e54..33fdf86 100644
--- a/gcc/testsuite/c-c++-common/pr68657-1.c
+++ b/gcc/testsuite/c-c++-common/pr68657-1.c
@@ -5,14 +5,14 @@
 void
 f1 (void)
 {
-  unsigned int a = -5; /* { dg-error "negative integer implicitly
converted to unsigned type" } */
+  unsigned int a = -5; /* { dg-error "unsigned conversion from .int. to
.unsigned int. changes value from .-5. to .4294967291." } */



The more specific match would fail for targets with 16-bit int.  You need
to keep it less specific in this test (if you want to test the more
specific text as well, another test could be added for that, restricted to
the int32 effective-target).

(The changes to Wconversion-real-integer-3.C and
Wconversion-real-integer2.C are OK in that those tests are restricted to
int32plus, although in theory 64-bit int would be an issue there.)


+  /* According to 6.3.1.3 of C11:
+     -3-  Otherwise, the new type is signed and the value cannot be
+          represented in it; either the result is implementation-defined
+         or an implementation-defined signal is raised.
+
+     In GCC such conversios wrap and diagnosed by mentioning "overflow"
+     if the absolut value of the operand is in excess of the maximum of
+     the destination of type, and "conversion" otherwise, as follows:
*/



s/conversios/conversions/; s/absolut/absolute/

OK with those changes.



Thanks for the careful review!  Done and committed in r248431.



Hi,

I have noticed failures on arm*:
  Executed from: gcc.dg/fixed-point/fixed-point.exp
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 12)
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 13)
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 14)
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 15)
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 16)
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 17)
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 18)
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 19)
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 20)
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 21)
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 22)
    gcc.dg/fixed-point/int-warning.c  (test for warnings, line 23)
    gcc.dg/fixed-point/int-warning.c (test for excess errors)

Excess errors:
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:12:8:
warning: overflow in conversion from '_Accum' to 'signed char' chages
value from '5.0e+2' to '-12' [-Woverflow]
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:13:8:
warning: overflow in conversion from '_Accum' to 'signed char' chages
value from '-5.0e+2' to '12' [-Woverflow]
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:14:8:
warning: overflow in conversion from 'long _Accum' to 'signed char'
chages value from '5.0e+2' to '-12' [-Woverflow]
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:15:8:
warning: overflow in conversion from 'long _Accum' to 'signed char'
chages value from '-5.0e+2' to '12' [-Woverflow]
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:16:8:
warning: overflow in conversion from 'long long _Accum' to 'signed
char' chages value from '5.0e+2' to '-12' [-Woverflow]
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:17:8:
warning: overflow in conversion from 'long long _Accum' to 'signed
char' chages value from '-5.0e+2' to '12' [-Woverflow]
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:18:8:
warning: overflow in conversion from '_Accum' to 'unsigned char'
chages value from '5.0e+2' to '244' [-Woverflow]
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:19:8:
warning: overflow in conversion from '_Accum' to 'unsigned char'
chages value from '-5.0e+2' to '12' [-Woverflow]
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:20:8:
warning: overflow in conversion from 'long _Accum' to 'unsigned char'
chages value from '5.0e+2' to '244' [-Woverflow]
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:21:8:
warning: overflow in conversion from 'long _Accum' to 'unsigned char'
chages value from '-5.0e+2' to '12' [-Woverflow]
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:22:8:
warning: overflow in conversion from 'long long _Accum' to 'unsigned
char' chages value from '5.0e+2' to '244' [-Woverflow]
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/fixed-point/int-warning.c:23:8:
warning: overflow in conversion from 'long long _Accum' to 'unsigned
char' chages value from '-5.0e+2' to '12' [-Woverflow]

Still present at r248552.


Both of these should be fixed by r248700..

Martin
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