What's the purpose of “for(;;)” [duplicate]

This question already has an answer here:

Endless loop in C/C++ [closed]

12 answers

In an old codebase, I found the following snippet:

for(;;){

  // code that manipulates a vector 'vec'

  if(vec.empty()) break;

}

Is there any purpose or convention behind using for(;;) instead of while(true), except for personal taste of the respective author?

asked Nov 21 '18 at 13:46

Michael

3,06612150

marked as duplicate by Hans Passant, llllllllll, StoryTeller c++
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Nov 21 '18 at 15:47

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1

Nope, these days it's just personal taste.

– Some programmer dude
Nov 21 '18 at 13:48

4

Four keys less to press :-)

– axiac
Nov 21 '18 at 13:48

And then there's this stackoverflow.com/questions/224138/infinite-loops-top-or-bottom

– StoryTeller
Nov 21 '18 at 13:48

3

I remember seeing while (true) throwing a warning regarding conditional depending on constant expression (or something similar), while using some compiler, where for (;;) wouldn't do that.

– Algirdas Preidžius
Nov 21 '18 at 13:49

3

Canonical: stackoverflow.com/questions/20186809/endless-loop-in-c-c

– Hans Passant
Nov 21 '18 at 13:52

|
show 1 more comment

This question already has an answer here:

Endless loop in C/C++ [closed]

12 answers

In an old codebase, I found the following snippet:

for(;;){

  // code that manipulates a vector 'vec'

  if(vec.empty()) break;

}

Is there any purpose or convention behind using for(;;) instead of while(true), except for personal taste of the respective author?

asked Nov 21 '18 at 13:46

Michael

3,06612150

marked as duplicate by Hans Passant, llllllllll, StoryTeller c++
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Nov 21 '18 at 15:47

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1

Nope, these days it's just personal taste.

– Some programmer dude
Nov 21 '18 at 13:48

4

Four keys less to press :-)

– axiac
Nov 21 '18 at 13:48

And then there's this stackoverflow.com/questions/224138/infinite-loops-top-or-bottom

– StoryTeller
Nov 21 '18 at 13:48

3

I remember seeing while (true) throwing a warning regarding conditional depending on constant expression (or something similar), while using some compiler, where for (;;) wouldn't do that.

– Algirdas Preidžius
Nov 21 '18 at 13:49

3

Canonical: stackoverflow.com/questions/20186809/endless-loop-in-c-c

– Hans Passant
Nov 21 '18 at 13:52

|
show 1 more comment

This question already has an answer here:

Endless loop in C/C++ [closed]

12 answers

In an old codebase, I found the following snippet:

for(;;){

  // code that manipulates a vector 'vec'

  if(vec.empty()) break;

}

Is there any purpose or convention behind using for(;;) instead of while(true), except for personal taste of the respective author?

asked Nov 21 '18 at 13:46

Michael

3,06612150

This question already has an answer here:

Endless loop in C/C++ [closed]

12 answers

In an old codebase, I found the following snippet:

for(;;){

  // code that manipulates a vector 'vec'

  if(vec.empty()) break;

}

Is there any purpose or convention behind using for(;;) instead of while(true), except for personal taste of the respective author?

This question already has an answer here:

Endless loop in C/C++ [closed]

12 answers

c++

asked Nov 21 '18 at 13:46

Michael

3,06612150

asked Nov 21 '18 at 13:46

Michael

3,06612150

asked Nov 21 '18 at 13:46

Michael

3,06612150

asked Nov 21 '18 at 13:46

Michael

3,06612150

asked Nov 21 '18 at 13:46

Michael

3,06612150

marked as duplicate by Hans Passant, llllllllll, StoryTeller c++
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Nov 21 '18 at 15:47

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

marked as duplicate by Hans Passant, llllllllll, StoryTeller c++
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Nov 21 '18 at 15:47

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1

Nope, these days it's just personal taste.

– Some programmer dude
Nov 21 '18 at 13:48

4

Four keys less to press :-)

– axiac
Nov 21 '18 at 13:48

And then there's this stackoverflow.com/questions/224138/infinite-loops-top-or-bottom

– StoryTeller
Nov 21 '18 at 13:48

3

I remember seeing while (true) throwing a warning regarding conditional depending on constant expression (or something similar), while using some compiler, where for (;;) wouldn't do that.

– Algirdas Preidžius
Nov 21 '18 at 13:49

3

Canonical: stackoverflow.com/questions/20186809/endless-loop-in-c-c

– Hans Passant
Nov 21 '18 at 13:52

|
show 1 more comment

1

Nope, these days it's just personal taste.

– Some programmer dude
Nov 21 '18 at 13:48

4

Four keys less to press :-)

– axiac
Nov 21 '18 at 13:48

And then there's this stackoverflow.com/questions/224138/infinite-loops-top-or-bottom

– StoryTeller
Nov 21 '18 at 13:48

3

I remember seeing while (true) throwing a warning regarding conditional depending on constant expression (or something similar), while using some compiler, where for (;;) wouldn't do that.

– Algirdas Preidžius
Nov 21 '18 at 13:49

3

Canonical: stackoverflow.com/questions/20186809/endless-loop-in-c-c

– Hans Passant
Nov 21 '18 at 13:52

Nope, these days it's just personal taste.

– Some programmer dude
Nov 21 '18 at 13:48

Four keys less to press :-)

– axiac
Nov 21 '18 at 13:48

And then there's this stackoverflow.com/questions/224138/infinite-loops-top-or-bottom

– StoryTeller
Nov 21 '18 at 13:48

I remember seeing while (true) throwing a warning regarding conditional depending on constant expression (or something similar), while using some compiler, where for (;;) wouldn't do that.

– Algirdas Preidžius
Nov 21 '18 at 13:49

Canonical: stackoverflow.com/questions/20186809/endless-loop-in-c-c

– Hans Passant
Nov 21 '18 at 13:52

|
show 1 more comment

2 Answers
2

active

oldest

votes

Older C++ compilers would not issue a warning for for(;;) but they would for while(true). Ditto for C, but with while(1).

Thus the convention stuck.

answered Nov 21 '18 at 13:50

Bathsheba

179k27254380

1

Interesting - presumably some "condition always evaluates to true" warning "inherited" from more complex expressions and not given a special case in the way that a totally empty condition (permissible only for a for) apparently was.

– Lightness Races in Orbit
Nov 21 '18 at 13:51

1

I'm not sure what should constitute a bug fix for such a compiler

– StoryTeller
Nov 21 '18 at 13:51

1

This is a good historical perspective. If you add that the statements are semantically equivalent, QoI aside, I'll just delete my answer as redundant

– Lightness Races in Orbit
Nov 21 '18 at 13:51

According to the accepted answer linked by Hans Passant in comments, the reason for(;;) is legal code is that the empty second expression is replaced by a nonzero constant. Presumably the compiler that makes that replacement assumes that it is intentional on the part of the programmer, which is why no diagnostic is issued.

– Tim Randall
Nov 21 '18 at 14:02

@TimRandall: Methinks it's simpler than that: the "expressions" in the for loop (or whatever they are called these days), can be optionally present or absent leading to 8 different possibilities. Deciding on which combinations would yield warnings would have been tedious, particularly in the old days.

– Bathsheba
Nov 21 '18 at 14:05

|
show 1 more comment

No.

It is personal taste only.

It is entirely equivalent to a while (true).

answered Nov 21 '18 at 13:49

Lightness Races in Orbit

290k51470801

add a comment |

2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

Older C++ compilers would not issue a warning for for(;;) but they would for while(true). Ditto for C, but with while(1).

Thus the convention stuck.

answered Nov 21 '18 at 13:50

Bathsheba

179k27254380

1

Interesting - presumably some "condition always evaluates to true" warning "inherited" from more complex expressions and not given a special case in the way that a totally empty condition (permissible only for a for) apparently was.

– Lightness Races in Orbit
Nov 21 '18 at 13:51

1

I'm not sure what should constitute a bug fix for such a compiler

– StoryTeller
Nov 21 '18 at 13:51

1

This is a good historical perspective. If you add that the statements are semantically equivalent, QoI aside, I'll just delete my answer as redundant

– Lightness Races in Orbit
Nov 21 '18 at 13:51

According to the accepted answer linked by Hans Passant in comments, the reason for(;;) is legal code is that the empty second expression is replaced by a nonzero constant. Presumably the compiler that makes that replacement assumes that it is intentional on the part of the programmer, which is why no diagnostic is issued.

– Tim Randall
Nov 21 '18 at 14:02

@TimRandall: Methinks it's simpler than that: the "expressions" in the for loop (or whatever they are called these days), can be optionally present or absent leading to 8 different possibilities. Deciding on which combinations would yield warnings would have been tedious, particularly in the old days.

– Bathsheba
Nov 21 '18 at 14:05

|
show 1 more comment

Older C++ compilers would not issue a warning for for(;;) but they would for while(true). Ditto for C, but with while(1).

Thus the convention stuck.

answered Nov 21 '18 at 13:50

Bathsheba

179k27254380

1

Interesting - presumably some "condition always evaluates to true" warning "inherited" from more complex expressions and not given a special case in the way that a totally empty condition (permissible only for a for) apparently was.

– Lightness Races in Orbit
Nov 21 '18 at 13:51

1

I'm not sure what should constitute a bug fix for such a compiler

– StoryTeller
Nov 21 '18 at 13:51

1

This is a good historical perspective. If you add that the statements are semantically equivalent, QoI aside, I'll just delete my answer as redundant

– Lightness Races in Orbit
Nov 21 '18 at 13:51

According to the accepted answer linked by Hans Passant in comments, the reason for(;;) is legal code is that the empty second expression is replaced by a nonzero constant. Presumably the compiler that makes that replacement assumes that it is intentional on the part of the programmer, which is why no diagnostic is issued.

– Tim Randall
Nov 21 '18 at 14:02

@TimRandall: Methinks it's simpler than that: the "expressions" in the for loop (or whatever they are called these days), can be optionally present or absent leading to 8 different possibilities. Deciding on which combinations would yield warnings would have been tedious, particularly in the old days.

– Bathsheba
Nov 21 '18 at 14:05

|
show 1 more comment

Older C++ compilers would not issue a warning for for(;;) but they would for while(true). Ditto for C, but with while(1).

Thus the convention stuck.

answered Nov 21 '18 at 13:50

Bathsheba

179k27254380

Older C++ compilers would not issue a warning for for(;;) but they would for while(true). Ditto for C, but with while(1).

Thus the convention stuck.

answered Nov 21 '18 at 13:50

Bathsheba

179k27254380

answered Nov 21 '18 at 13:50

Bathsheba

179k27254380

answered Nov 21 '18 at 13:50

Bathsheba

179k27254380

answered Nov 21 '18 at 13:50

Bathsheba

179k27254380

1

Interesting - presumably some "condition always evaluates to true" warning "inherited" from more complex expressions and not given a special case in the way that a totally empty condition (permissible only for a for) apparently was.

– Lightness Races in Orbit
Nov 21 '18 at 13:51

1

I'm not sure what should constitute a bug fix for such a compiler

– StoryTeller
Nov 21 '18 at 13:51

1

This is a good historical perspective. If you add that the statements are semantically equivalent, QoI aside, I'll just delete my answer as redundant

– Lightness Races in Orbit
Nov 21 '18 at 13:51

According to the accepted answer linked by Hans Passant in comments, the reason for(;;) is legal code is that the empty second expression is replaced by a nonzero constant. Presumably the compiler that makes that replacement assumes that it is intentional on the part of the programmer, which is why no diagnostic is issued.

– Tim Randall
Nov 21 '18 at 14:02

@TimRandall: Methinks it's simpler than that: the "expressions" in the for loop (or whatever they are called these days), can be optionally present or absent leading to 8 different possibilities. Deciding on which combinations would yield warnings would have been tedious, particularly in the old days.

– Bathsheba
Nov 21 '18 at 14:05

|
show 1 more comment

1

Interesting - presumably some "condition always evaluates to true" warning "inherited" from more complex expressions and not given a special case in the way that a totally empty condition (permissible only for a for) apparently was.

– Lightness Races in Orbit
Nov 21 '18 at 13:51

1

I'm not sure what should constitute a bug fix for such a compiler

– StoryTeller
Nov 21 '18 at 13:51

1

This is a good historical perspective. If you add that the statements are semantically equivalent, QoI aside, I'll just delete my answer as redundant

– Lightness Races in Orbit
Nov 21 '18 at 13:51

According to the accepted answer linked by Hans Passant in comments, the reason for(;;) is legal code is that the empty second expression is replaced by a nonzero constant. Presumably the compiler that makes that replacement assumes that it is intentional on the part of the programmer, which is why no diagnostic is issued.

– Tim Randall
Nov 21 '18 at 14:02

@TimRandall: Methinks it's simpler than that: the "expressions" in the for loop (or whatever they are called these days), can be optionally present or absent leading to 8 different possibilities. Deciding on which combinations would yield warnings would have been tedious, particularly in the old days.

– Bathsheba
Nov 21 '18 at 14:05

Interesting - presumably some "condition always evaluates to true" warning "inherited" from more complex expressions and not given a special case in the way that a totally empty condition (permissible only for a for) apparently was.

– Lightness Races in Orbit
Nov 21 '18 at 13:51

I'm not sure what should constitute a bug fix for such a compiler

– StoryTeller
Nov 21 '18 at 13:51

This is a good historical perspective. If you add that the statements are semantically equivalent, QoI aside, I'll just delete my answer as redundant

– Lightness Races in Orbit
Nov 21 '18 at 13:51

According to the accepted answer linked by Hans Passant in comments, the reason for(;;) is legal code is that the empty second expression is replaced by a nonzero constant. Presumably the compiler that makes that replacement assumes that it is intentional on the part of the programmer, which is why no diagnostic is issued.

– Tim Randall
Nov 21 '18 at 14:02

@TimRandall: Methinks it's simpler than that: the "expressions" in the for loop (or whatever they are called these days), can be optionally present or absent leading to 8 different possibilities. Deciding on which combinations would yield warnings would have been tedious, particularly in the old days.

– Bathsheba
Nov 21 '18 at 14:05

|
show 1 more comment

No.

It is personal taste only.

It is entirely equivalent to a while (true).

answered Nov 21 '18 at 13:49

Lightness Races in Orbit

290k51470801

add a comment |

No.

It is personal taste only.

It is entirely equivalent to a while (true).

answered Nov 21 '18 at 13:49

Lightness Races in Orbit

290k51470801

add a comment |

No.

It is personal taste only.

It is entirely equivalent to a while (true).

answered Nov 21 '18 at 13:49

Lightness Races in Orbit

290k51470801

No.

It is personal taste only.

It is entirely equivalent to a while (true).

answered Nov 21 '18 at 13:49

Lightness Races in Orbit

290k51470801

answered Nov 21 '18 at 13:49

Lightness Races in Orbit

290k51470801

answered Nov 21 '18 at 13:49

Lightness Races in Orbit

290k51470801

answered Nov 21 '18 at 13:49

Lightness Races in Orbit

290k51470801

add a comment |

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