[Bug other/23572] No warning for assigning a value to a 'float' variable that overflows with option -Wextra
--- Additional Comments From qiyaoltc at cn dot ibm dot com 2005-08-29
02:57 ---
OK.
GCC version: 3.4.3 20050227 (Red Hat 3.4.3-22.1)
GNU C Library: stable release version 2.3.4
OS : Red Hat Enterprise Linux AS release 4 (Nahant Update 1)
I write a small example named overflow-test.c, here is the source code:
1 #includestdio.h
2 int main()
3 {
4 /* overflow. */
5 float f1 = 3.5E+38;
6 /* underflow. */
7 float f2 = 3.3E-46;
8 /* overflow. */
9 double d1 = 1.9E+308;
10 /* underflow. */
11 double d2 = 1.4E-325;
12 /* overflow, 2**32. */
13 int i = 4294967296;
14
15 printf(%e,%e,%e,%e\n,f1,f2,d1,d2);
16 printf(%d\n,i);
17 return 0;
18 }
And I compile it like this:
[EMAIL PROTECTED] gcc -o overflow-test -Wextra -Wall -g overflow-test.c
overflow-test.c: In function `main':
overflow-test.c:13: warning: integer constant is too large for long type
overflow-test.c:13: warning: overflow in implicit constant conversion
I run it,
[EMAIL PROTECTED] ./overflow-test
inf,0.00e+00,inf,0.00e+00
0
I hope this example would be helpful. Any comments are highly aprreciated!
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23572
[Bug other/23572] No warning for assigning a value to a 'float' variable that overflows with option -Wextra
--- Additional Comments From qiyaoltc at cn dot ibm dot com 2005-08-29 05:00 --- I add suffix f to the end of float constants at line 5 and line 7, and add option -pedantic, the output from gcc is like this: overflow-test.c:5: warning: floating constant exceeds range of float overflow-test.c:9: warning: floating constant exceeds range of double overflow-test.c:13: warning: integer constant is too large for long type overflow-test.c:13: warning: overflow in implicit constant conversion It seems that gcc has checked initialization which caused overflow, but do not check underflow, that is to say: 1 GCC does not check underflow event, at least options -pedantic does not enable underflow check. 2 If there is some mechanism in GCC internal to check underflow and overflow, there is a bug in gcc info about the description of -Wextra option. Could you tell me what I could do to this problem? Maybe, it is impossible for me to fix it, but I just want to do something more. Please give me some suggestions and I will try to do it. Thanks. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23572
[Bug other/23572] New: No warning for assigning a value to a 'float' variable that overflows with option -Wextra
I tried compilers 4.1.0 through mainline and none of them warn about nitializing a float variable with a value that will overflow, underflow, or lose precision for -W or -Wextra. But in GCC info, It is said like this: in GCC info(GCC 3.3.4). `-Wextra' (This option used to be called `-W'. The older name is still supported, but the newer name is more descriptive.) Print extra warning messages for these events: * Any of several floating-point events that often indicate errors, such as overflow, underflow, loss of precision, etc. Is this a bug either in GCC or a bug in documentation? -- Summary: No warning for assigning a value to a 'float' variable that overflows with option -Wextra Product: gcc Version: 4.1.0 Status: UNCONFIRMED Severity: normal Priority: P2 Component: other AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: qiyaoltc at cn dot ibm dot com CC: gcc-bugs at gcc dot gnu dot org,janis187 at us dot ibm dot com GCC build triplet: ppc64-redhat-linux GCC host triplet: ppc64-redhat-linux GCC target triplet: ppc64-redhat-linux http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23572
