Re: Constants and undefined behavior

Liste des GroupesRevenir à cl c  
Sujet : Re: Constants and undefined behavior
De : janis_papanagnou+ng (at) *nospam* hotmail.com (Janis Papanagnou)
Groupes : comp.lang.c
Date : 11. Jun 2026, 16:45:31
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <110el6r$1nauc$7@dont-email.me>
References : 1 2 3 4 5
User-Agent : Mozilla Thunderbird
On 2026-06-10 16:37, Dan Cross wrote:
[...]
Here's a C version with the same behavior:
 ```
term% cat weird.c
#include <stdio.h>
 int
main(void)
{
         for (unsigned int k = 0; k != 1; k += 2)
                 ;
return 0;
}
 void
hello(void)
{
         printf("Hello, World!\n");
}
term% clang --version
clang version 22.1.6
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
term% clang -Wall -pedantic -O1 -std=c23 -o weird weird.c
term% ./weird
Hello, World!
term%
```
Wow, that's really fascinating! (In a bad sense.)
And (in clang) just an effect of the '-O1' (as I notice).
I may have missed the "programming language design" wisdom of the
past decades. Back then we had the conception that "optimization"
is a method to transform a program to a _functionally equivalent_
code (one that is faster, requires less memory, or some such).
Janis

[...]

Date Sujet#  Auteur
27 May 26 * this girl calls c ugly365fir
27 May 26 `* Re: this girl calls c ugly364fir
28 May 26  `* Re: this girl calls c ugly363BGB
28 May 26   +* Re: this girl calls c ugly5Lawrence D’Oliveiro
28 May 26   i+* Re: this girl calls c ugly3BGB
29 May 26   ii`* Re: this girl calls c ugly2Lawrence D’Oliveiro
29 May 26   ii `- Re: this girl calls c ugly1BGB
28 May 26   i`- Re: this girl calls c ugly1Bonita Montero
28 May 26   +* Re: this girl calls c ugly19Janis Papanagnou
28 May 26   i+* Re: this girl calls c ugly15BGB
29 May 26   ii+- Re: this girl calls c ugly1Lawrence D’Oliveiro
29 May 26   ii`* Re: this girl calls c ugly13Janis Papanagnou
29 May 26   ii `* Re: this girl calls c ugly12BGB
29 May 26   ii  +* Re: this girl calls c ugly9David Brown
29 May 26   ii  i`* Re: this girl calls c ugly8BGB
30 May 26   ii  i `* Re: this girl calls c ugly7David Brown
30 May 26   ii  i  +* Re: this girl calls c ugly2Janis Papanagnou
30 May 26   ii  i  i`- Re: this girl calls c ugly1David Brown
30 May 26   ii  i  `* Re: this girl calls c ugly4BGB
31 May 26   ii  i   `* Re: this girl calls c ugly3David Brown
31 May 26   ii  i    `* Re: this girl calls c ugly2BGB
31 May 26   ii  i     `- Re: this girl calls c ugly1David Brown
29 May 26   ii  +- Re: this girl calls c ugly1Janis Papanagnou
30 May 26   ii  `- Re: this girl calls c ugly1Lawrence D’Oliveiro
28 May 26   i`* Re: this girl calls c ugly3Chris M. Thomasson
29 May 26   i `* Re: this girl calls c ugly2Janis Papanagnou
29 May 26   i  `- Re: this girl calls c ugly1Chris M. Thomasson
28 May 26   `* Re: this girl calls c ugly338fir
28 May 26    `* Re: this girl calls c ugly337BGB
29 May 26     +* Re: this girl calls c ugly330Lawrence D’Oliveiro
29 May 26     i`* Re: this girl calls c ugly329Janis Papanagnou
29 May 26     i `* Re: this girl calls c ugly328Bart
29 May 26     i  +* Re: this girl calls c ugly312Janis Papanagnou
29 May 26     i  i`* Re: this girl calls c ugly311Bart
29 May 26     i  i +* Re: this girl calls c ugly9Janis Papanagnou
29 May 26     i  i i+* Re: this girl calls c ugly2Bart
29 May 26     i  i ii`- Re: this girl calls c ugly1Janis Papanagnou
29 May 26     i  i i`* Re: this girl calls c ugly6Bart
29 May 26     i  i i +* Re: this girl calls c ugly4Janis Papanagnou
29 May 26     i  i i i`* Re: this girl calls c ugly3Bart
29 May 26     i  i i i `* Re: this girl calls c ugly2Janis Papanagnou
29 May 26     i  i i i  `- Re: this girl calls c ugly1Bart
29 May 26     i  i i `- Re: this girl calls c ugly1Keith Thompson
29 May 26     i  i `* Re: this girl calls c ugly301tTh
29 May 26     i  i  `* Re: this girl calls c ugly300Bart
29 May 26     i  i   +* Re: this girl calls c ugly298Keith Thompson
29 May 26     i  i   i`* Re: this girl calls c ugly297Bart
29 May 26     i  i   i +- Re: this girl calls c ugly1Janis Papanagnou
29 May 26     i  i   i `* Re: this girl calls c ugly295Keith Thompson
29 May 26     i  i   i  `* Re: this girl calls c ugly294Bart
29 May 26     i  i   i   +* Re: this girl calls c ugly5Keith Thompson
30 May 26     i  i   i   i`* Re: this girl calls c ugly4James Kuyper
30 May 26     i  i   i   i `* Re: this girl calls c ugly3Bart
30 May 26     i  i   i   i  `* Re: this girl calls c ugly2Keith Thompson
30 May 26     i  i   i   i   `- Re: this girl calls c ugly1Bart
30 May 26     i  i   i   `* Re: this girl calls c ugly288Dan Cross
30 May 26     i  i   i    +* Re: this girl calls c ugly284Bart
31 May 26     i  i   i    i+* Re: this girl calls c ugly282Keith Thompson
31 May 26     i  i   i    ii+* Re: this girl calls c ugly5Janis Papanagnou
31 May 26     i  i   i    iii+* Re: this girl calls c ugly2Keith Thompson
2 Jun 26     i  i   i    iiii`- Re: this girl calls c ugly1Janis Papanagnou
31 May 26     i  i   i    iii`* Re: this girl calls c ugly2David Brown
2 Jun 26     i  i   i    iii `- Re: this girl calls c ugly1Janis Papanagnou
31 May 26     i  i   i    ii`* Re: this girl calls c ugly276Richard Harnden
31 May 26     i  i   i    ii +* Re: this girl calls c ugly171David Brown
31 May 26     i  i   i    ii i+* Re: this girl calls c ugly168Bart
31 May 26     i  i   i    ii ii+* Re: this girl calls c ugly142David Brown
31 May 26     i  i   i    ii iii`* Re: this girl calls c ugly141James Kuyper
31 May 26     i  i   i    ii iii `* Re: this girl calls c ugly140David Brown
31 May 26     i  i   i    ii iii  +* Re: this girl calls c ugly4James Kuyper
31 May 26     i  i   i    ii iii  i`* Re: this girl calls c ugly3David Brown
31 May 26     i  i   i    ii iii  i `* Re: this girl calls c ugly2James Kuyper
1 Jun 26     i  i   i    ii iii  i  `- Re: this girl calls c ugly1David Brown
31 May 26     i  i   i    ii iii  `* Re: this girl calls c ugly135Keith Thompson
1 Jun 26     i  i   i    ii iii   +* Re: this girl calls c ugly2David Brown
1 Jun 26     i  i   i    ii iii   i`- Re: this girl calls c ugly1Keith Thompson
2 Jun 26     i  i   i    ii iii   +* Re: this girl calls c ugly131Janis Papanagnou
2 Jun 26     i  i   i    ii iii   i+- Re: this girl calls c ugly1James Kuyper
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2 Jun 26     i  i   i    ii iii   ii`* Re: Constants and undefined behavior83Dan Cross
4 Jun 26     i  i   i    ii iii   ii `* Re: Constants and undefined behavior82Tim Rentsch
4 Jun 26     i  i   i    ii iii   ii  `* Re: Constants and undefined behavior81Dan Cross
4 Jun 26     i  i   i    ii iii   ii   +* Re: Constants and undefined behavior31Keith Thompson
5 Jun 26     i  i   i    ii iii   ii   i+* Re: Constants and undefined behavior28Dan Cross
5 Jun 26     i  i   i    ii iii   ii   ii+* Re: Constants and undefined behavior24Keith Thompson
6 Jun 26     i  i   i    ii iii   ii   iii+* Re: Constants and undefined behavior19Dan Cross
6 Jun 26     i  i   i    ii iii   ii   iiii`* Re: Constants and undefined behavior18Keith Thompson
8 Jun 26     i  i   i    ii iii   ii   iiii `* Re: Constants and undefined behavior17Dan Cross
8 Jun 26     i  i   i    ii iii   ii   iiii  +* Re: Constants and undefined behavior5Keith Thompson
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9 Jun 26     i  i   i    ii iii   ii   iiii   +* Re: Constants and undefined behavior3James Kuyper
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11 Jun 26     i  i   i    ii iii   ii   iiii   `* Re: Constants and undefined behavior7Janis Papanagnou
11 Jun 26     i  i   i    ii iii   ii   iiii    +* Re: Constants and undefined behavior2Dan Cross
11 Jun 26     i  i   i    ii iii   ii   iiii    i`- Re: Constants and undefined behavior1Janis Papanagnou
11 Jun 26     i  i   i    ii iii   ii   iiii    `* Re: Constants and undefined behavior4Waldek Hebisch
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7 Jun 26     i  i   i    ii iii   ii   i`* Re: Constants and undefined behavior2Tim Rentsch
9 Jun 26     i  i   i    ii iii   ii   `* Re: Constants and undefined behavior49Tim Rentsch
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2 Jun 26     i  i   i    ii iii   `- Re: this girl calls c ugly1Chris M. Thomasson
2 Jun 26     i  i   i    ii ii`* Re: this girl calls c ugly25Dan Cross
31 May 26     i  i   i    ii i`* Re: this girl calls c ugly2James Kuyper
31 May 26     i  i   i    ii +* Re: this girl calls c ugly2Keith Thompson
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31 May 26     i  i   i    i`- Re: this girl calls c ugly1Dan Cross
1 Jun 26     i  i   i    `* Re: this girl calls c ugly3Tim Rentsch
30 May 26     i  i   `- Re: this girl calls c ugly1David Brown
29 May 26     i  +* Re: this girl calls c ugly6Janis Papanagnou
30 May 26     i  `* Re: this girl calls c ugly9Lawrence D’Oliveiro
29 May 26     `* Re: this girl calls c ugly6Bonita Montero

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