* tolower function
@ 1999-06-08 17:27 Peter Kabal
1999-06-08 18:35 ` J. J. Farrell
1999-06-30 22:10 ` Peter Kabal
0 siblings, 2 replies; 4+ messages in thread
From: Peter Kabal @ 1999-06-08 17:27 UTC (permalink / raw)
To: cygwin
In an early version of a function to convert a string to lowercase, I did
not properly convert the input (signed) characters to unsigned before
handing them off to the tolower function. I discovered that tolower behaves
oddly for negative input values. For instance tolower(-32) returns zero,
while tolower(-31) returns -31.
Perhaps tolower should be fixed to behave "properly" for "improper" inputs.
-----------------------
Under cygwin B20.1, the test program which appears below prints out the
following.
0X64 (2:0) => 0X64
0X44 (0:1) => 0X64
0XFFFFFFE1 (0:0) => 0XFFFFFFE1
0XFFFFFFE0 (2:1) => 0X00
0XFFFFFFDF (0:1) => 0XFFFFFFFF
Running gcc on a Solaris system gives a different result.
0X64 (2:0) => 0X64
0X44 (0:1) => 0X64
0XFFFFFFE1 (2:0) => 0XFFFFFFE1
0XFFFFFFE0 (2:0) => 0XFFFFFFE0
0XFFFFFFDF (0:0) => 0XFFFFFFDF
(This one is suspicious, an seemingly innocuous change to print out the
first two values changed the third line islower value from 0 to 2!).
Finally running the Sun compiler on a Solaris system gives the following,
seemingly more reasonable result.
0X64 (2:0) => 0X64
0X44 (0:1) => 0X64
0XFFFFFFE1 (0:0) => 0XFFFFFFE1
0XFFFFFFE0 (0:0) => 0XFFFFFFE0
0XFFFFFFDF (0:0) => 0XFFFFFFDF
==============================
#include <ctype.h>
#include <stdio.h>
int main (int argc, const char argv[])
{
int i;
i = 'd';
printf ("0X%.2X (%d:%d) => 0X%.2X\n", i, islower(i), isupper(i),
tolower(i));
i = 'D';
printf ("0X%.2X (%d:%d) => 0X%.2X\n", i, islower(i), isupper(i),
tolower(i));
i = -31;
printf ("0X%.2X (%d:%d) => 0X%.2X\n", i, islower(i), isupper(i),
tolower(i));
i = -32;
printf ("0X%.2X (%d:%d) => 0X%.2X\n", i, islower(i), isupper(i),
tolower(i));
i = -33;
printf ("0X%.2X (%d:%d) => 0X%.2X\n", i, islower(i), isupper(i),
tolower(i));
return 0;
}
--
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: tolower function
1999-06-08 17:27 tolower function Peter Kabal
@ 1999-06-08 18:35 ` J. J. Farrell
1999-06-30 22:10 ` J. J. Farrell
1999-06-30 22:10 ` Peter Kabal
1 sibling, 1 reply; 4+ messages in thread
From: J. J. Farrell @ 1999-06-08 18:35 UTC (permalink / raw)
To: cygwin
> From: "Peter Kabal" <kabal@ece.mcgill.ca>
>
> In an early version of a function to convert a string to lowercase, I did
> not properly convert the input (signed) characters to unsigned before
> handing them off to the tolower function. I discovered that tolower behaves
> oddly for negative input values. For instance tolower(-32) returns zero,
> while tolower(-31) returns -31.
>
> Perhaps tolower should be fixed to behave "properly" for "improper" inputs.
That's easily done by defining it's current behaviour as
proper, as an extension to C!
The value of the parameter to the ctype functions must be
representable as an unsigned char, or must be EOF. Any other
value results in undefined behavior.
Contributors efforts are probably better spent enhancing the
functionality rather than extending standard interfaces to
make incorrect code behave in some predictable way.
--
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^ permalink raw reply [flat|nested] 4+ messages in thread
* tolower function
1999-06-08 17:27 tolower function Peter Kabal
1999-06-08 18:35 ` J. J. Farrell
@ 1999-06-30 22:10 ` Peter Kabal
1 sibling, 0 replies; 4+ messages in thread
From: Peter Kabal @ 1999-06-30 22:10 UTC (permalink / raw)
To: cygwin
In an early version of a function to convert a string to lowercase, I did
not properly convert the input (signed) characters to unsigned before
handing them off to the tolower function. I discovered that tolower behaves
oddly for negative input values. For instance tolower(-32) returns zero,
while tolower(-31) returns -31.
Perhaps tolower should be fixed to behave "properly" for "improper" inputs.
-----------------------
Under cygwin B20.1, the test program which appears below prints out the
following.
0X64 (2:0) => 0X64
0X44 (0:1) => 0X64
0XFFFFFFE1 (0:0) => 0XFFFFFFE1
0XFFFFFFE0 (2:1) => 0X00
0XFFFFFFDF (0:1) => 0XFFFFFFFF
Running gcc on a Solaris system gives a different result.
0X64 (2:0) => 0X64
0X44 (0:1) => 0X64
0XFFFFFFE1 (2:0) => 0XFFFFFFE1
0XFFFFFFE0 (2:0) => 0XFFFFFFE0
0XFFFFFFDF (0:0) => 0XFFFFFFDF
(This one is suspicious, an seemingly innocuous change to print out the
first two values changed the third line islower value from 0 to 2!).
Finally running the Sun compiler on a Solaris system gives the following,
seemingly more reasonable result.
0X64 (2:0) => 0X64
0X44 (0:1) => 0X64
0XFFFFFFE1 (0:0) => 0XFFFFFFE1
0XFFFFFFE0 (0:0) => 0XFFFFFFE0
0XFFFFFFDF (0:0) => 0XFFFFFFDF
==============================
#include <ctype.h>
#include <stdio.h>
int main (int argc, const char argv[])
{
int i;
i = 'd';
printf ("0X%.2X (%d:%d) => 0X%.2X\n", i, islower(i), isupper(i),
tolower(i));
i = 'D';
printf ("0X%.2X (%d:%d) => 0X%.2X\n", i, islower(i), isupper(i),
tolower(i));
i = -31;
printf ("0X%.2X (%d:%d) => 0X%.2X\n", i, islower(i), isupper(i),
tolower(i));
i = -32;
printf ("0X%.2X (%d:%d) => 0X%.2X\n", i, islower(i), isupper(i),
tolower(i));
i = -33;
printf ("0X%.2X (%d:%d) => 0X%.2X\n", i, islower(i), isupper(i),
tolower(i));
return 0;
}
--
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: tolower function
1999-06-08 18:35 ` J. J. Farrell
@ 1999-06-30 22:10 ` J. J. Farrell
0 siblings, 0 replies; 4+ messages in thread
From: J. J. Farrell @ 1999-06-30 22:10 UTC (permalink / raw)
To: cygwin
> From: "Peter Kabal" <kabal@ece.mcgill.ca>
>
> In an early version of a function to convert a string to lowercase, I did
> not properly convert the input (signed) characters to unsigned before
> handing them off to the tolower function. I discovered that tolower behaves
> oddly for negative input values. For instance tolower(-32) returns zero,
> while tolower(-31) returns -31.
>
> Perhaps tolower should be fixed to behave "properly" for "improper" inputs.
That's easily done by defining it's current behaviour as
proper, as an extension to C!
The value of the parameter to the ctype functions must be
representable as an unsigned char, or must be EOF. Any other
value results in undefined behavior.
Contributors efforts are probably better spent enhancing the
functionality rather than extending standard interfaces to
make incorrect code behave in some predictable way.
--
Want to unsubscribe from this list?
Send a message to cygwin-unsubscribe@sourceware.cygnus.com
^ permalink raw reply [flat|nested] 4+ messages in thread
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1999-06-08 17:27 tolower function Peter Kabal
1999-06-08 18:35 ` J. J. Farrell
1999-06-30 22:10 ` J. J. Farrell
1999-06-30 22:10 ` Peter Kabal
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