#pragma once in ISO standard yet?

[Rick]

I'm told that "#pragma once" has made it into the ISO standard for
either C or C++. I can't find any reference to that anywhere. If
it's true, do any of you have a reference I can use?

Thanks...

 

[Tomás Ó hÉilidhe]

I'm told that "#pragma once" has made it into the ISO standard for
either C or C++. I can't find any reference to that anywhere. If
it's true, do any of you have a reference I can use?

If it's either language it would be C++.

Try asking in comp.std.c++

 

[jacob navia]

I'm told that "#pragma once" has made it into the ISO standard for
either C or C++. I can't find any reference to that anywhere. If
it's true, do any of you have a reference I can use?

Thanks...

No, it is not in the standard. Many compilers implement this
but it is not (yet) standard

 

[Tor Rustad]

I'm told that "#pragma once" has made it into the ISO standard for
either C or C++. I can't find any reference to that anywhere. If
it's true, do any of you have a reference I can use?

You have been told wrong for C.

 

[Peter Nilsson]

Did you mean neither? It isn't in C. I doubt it's in C++.

Ask the person who told you to supply evidence.

No, it is not in the standard. Many compilers implement
this but it is not (yet) standard

Because many compilers implement it differently. The normal
include guard mechanism may be klunky, but at least the
programmer always knows _exactly_ what the preprocessor can
and will do with it.

 

[CBFalconer]

I'm told that "#pragma once" has made it into the ISO standard for
either C or C++. I can't find any reference to that anywhere. If
it's true, do any of you have a reference I can use?

For example, from N869.txt:

[1] c:\stds>cat n869.txt | grep -n #pragma
9468: #pragma STDC FP_CONTRACT on-off-switch
9469: #pragma STDC FENV_ACCESS on-off-switch
9470: #pragma STDC CX_LIMITED_RANGE on-off-switch
9588: #pragma listing on "..\listing.dir"
10114: #pragma STDC CX_LIMITED_RANGE on-off-switch
11136: #pragma STDC FENV_ACCESS on-off-switch
11179: #pragma STDC FENV_ACCESS ON
11192: placed invocation of #pragma STDC FENV_ACCESS ON.165)
11208: #pragma STDC FENV_ACCESS ON pragma, and assuming the
11338: #pragma STDC FENV_ACCESS ON
11405: #pragma STDC FENV_ACCESS ON
11526: #pragma STDC FENV_ACCESS ON
12343: #pragma STDC FP_CONTRACT on-off-switch
24253: #pragma STDC CX_LIMITED_RANGE on-off-switch
24349: #pragma STDC FENV_ACCESS on-off-switch
24452: #pragma STDC FP_CONTRACT on-off-switch
25641: #pragma STDC FENV_ACCESS ON
25680: #pragma STDC FENV_ACCESS ON
25752: #pragma STDC FENV_ACCESS ON
26310: #pragma STDC FENV_ACCESS ON
26461: #pragma STDC FENV_ACCESS ON
26514: #pragma STDC FENV_ACCESS ON
26564: #pragma STDC FENV_ACCESS ON
26825: #pragma STDC FP_CONTRACT OFF
26888: #pragma STDC FP_CONTRACT OFF
27783: -- An unrecognized #pragma directive is encountered
28363: -- A non-STDC #pragma preprocessing directive that is
28367: -- A #pragma STDC preprocessing directive does not match
29051: -- The behavior on each recognized non-STDC #pragma
29522: #pragma preprocessing directive, 6.10.6

 

[CBFalconer]

No, it is not in the standard. Many compilers implement this
but it is not (yet) standard

Wrong. It is in the C99 standard.

 

[Peter Nilsson]

Wrong. It is in the C99 standard.

Chapter and verse, please.

Note the OP is talking specifically about #pragma once, not
merely #pragma.

 

[Ian Collins]

I'm told that "#pragma once" has made it into the ISO standard for
either C or C++. I can't find any reference to that anywhere. If
it's true, do any of you have a reference I can use?

For example, from N869.txt:

[1] c:\stds>cat n869.txt | grep -n #pragma

What the OP wanted was more like

grep "#pragma" n869.txt | grep once

Which outputs a whole not of nothing....

 

[Martin Ambuhl]

Wrong. It is in the C99 standard.

Since all the C99 standard pragmas begin with
#pragma STDC
it is very difficult for
#pragma once
to be a C99 standard pragma. Would you care to share _where_ in the
standard you think this is? There are only three standard pragmas,
FP_CONTRACT, FENV_ACCESS, and CX_SELECTED_RANGE. None of them is
spelled "once".

 

[Chris Hills]

For example, from N869.txt:

Bearing in mind that an N document is NOT an ISO standard and the
contents of an N document could change completely en route to an ISO
standard.

It probably won't but.......

 

[James Kuyper]

Wrong. It is in the C99 standard.

It's not in my copy. What's the precise name of the document you're
using, and which section is it that describes #pragma once?

 

[James Kuyper]

I'm told that "#pragma once" has made it into the ISO standard for
either C or C++. I can't find any reference to that anywhere. If
it's true, do any of you have a reference I can use?

For example, from N869.txt:

[1] c:\stds>cat n869.txt | grep -n #pragma
9468: #pragma STDC FP_CONTRACT on-off-switch
9469: #pragma STDC FENV_ACCESS on-off-switch
9470: #pragma STDC CX_LIMITED_RANGE on-off-switch
9588: #pragma listing on "..\listing.dir"
10114: #pragma STDC CX_LIMITED_RANGE on-off-switch
11136: #pragma STDC FENV_ACCESS on-off-switch
11179: #pragma STDC FENV_ACCESS ON
11192: placed invocation of #pragma STDC FENV_ACCESS ON.165)
11208: #pragma STDC FENV_ACCESS ON pragma, and assuming the
11338: #pragma STDC FENV_ACCESS ON
11405: #pragma STDC FENV_ACCESS ON
11526: #pragma STDC FENV_ACCESS ON
12343: #pragma STDC FP_CONTRACT on-off-switch
24253: #pragma STDC CX_LIMITED_RANGE on-off-switch
24349: #pragma STDC FENV_ACCESS on-off-switch
24452: #pragma STDC FP_CONTRACT on-off-switch
25641: #pragma STDC FENV_ACCESS ON
25680: #pragma STDC FENV_ACCESS ON
25752: #pragma STDC FENV_ACCESS ON
26310: #pragma STDC FENV_ACCESS ON
26461: #pragma STDC FENV_ACCESS ON
26514: #pragma STDC FENV_ACCESS ON
26564: #pragma STDC FENV_ACCESS ON
26825: #pragma STDC FP_CONTRACT OFF
26888: #pragma STDC FP_CONTRACT OFF
27783: -- An unrecognized #pragma directive is encountered
28363: -- A non-STDC #pragma preprocessing directive that is
28367: -- A #pragma STDC preprocessing directive does not match
29051: -- The behavior on each recognized non-STDC #pragma
29522: #pragma preprocessing directive, 6.10.6

I don't see "#pragma once" anywhere in that list. If my eyes are
deceiving me, could you do something to make the location of the word
"once" more obvious?

 

[CBFalconer]

Since all the C99 standard pragmas begin with
#pragma STDC
it is very difficult for
#pragma once
to be a C99 standard pragma. Would you care to share _where_ in the
standard you think this is? There are only three standard pragmas,
FP_CONTRACT, FENV_ACCESS, and CX_SELECTED_RANGE. None of them is
spelled "once".

I extracted all occurences of "#pragma" in N869 in another
article. If you really want the " once" part it is missing, but
the data is there.

 

[CBFalconer]

Bearing in mind that an N document is NOT an ISO standard and the
contents of an N document could change completely en route to an ISO
standard.

This didn't and doesn't change.

 

[CBFalconer]

I'm told that "#pragma once" has made it into the ISO standard for
either C or C++. I can't find any reference to that anywhere. If
it's true, do any of you have a reference I can use?

For example, from N869.txt:

[1] c:\stds>cat n869.txt | grep -n #pragma
9468: #pragma STDC FP_CONTRACT on-off-switch
9469: #pragma STDC FENV_ACCESS on-off-switch
9470: #pragma STDC CX_LIMITED_RANGE on-off-switch
9588: #pragma listing on "..\listing.dir"
10114: #pragma STDC CX_LIMITED_RANGE on-off-switch
11136: #pragma STDC FENV_ACCESS on-off-switch
11179: #pragma STDC FENV_ACCESS ON
11192: placed invocation of #pragma STDC FENV_ACCESS ON.165)
11208: #pragma STDC FENV_ACCESS ON pragma, and assuming the
11338: #pragma STDC FENV_ACCESS ON
11405: #pragma STDC FENV_ACCESS ON
11526: #pragma STDC FENV_ACCESS ON
12343: #pragma STDC FP_CONTRACT on-off-switch
24253: #pragma STDC CX_LIMITED_RANGE on-off-switch
24349: #pragma STDC FENV_ACCESS on-off-switch
24452: #pragma STDC FP_CONTRACT on-off-switch
25641: #pragma STDC FENV_ACCESS ON
25680: #pragma STDC FENV_ACCESS ON
25752: #pragma STDC FENV_ACCESS ON
26310: #pragma STDC FENV_ACCESS ON
26461: #pragma STDC FENV_ACCESS ON
26514: #pragma STDC FENV_ACCESS ON
26564: #pragma STDC FENV_ACCESS ON
26825: #pragma STDC FP_CONTRACT OFF
26888: #pragma STDC FP_CONTRACT OFF
27783: -- An unrecognized #pragma directive is encountered
28363: -- A non-STDC #pragma preprocessing directive that is
28367: -- A #pragma STDC preprocessing directive does not match
29051: -- The behavior on each recognized non-STDC #pragma
29522: #pragma preprocessing directive, 6.10.6

I don't see "#pragma once" anywhere in that list. If my eyes are
deceiving me, could you do something to make the location of the
word "once" more obvious?

Did you thing that grep would miss such an occurence? It didn't.

 

[Chris Hills]

It's not in my copy. What's the precise name of the document you're
using, and which section is it that describes #pragma once?

He is quoting from N869.txt


However you have to bare in mind that an N document is NOT an ISO
standard and the contents of an N document could change completely en
route to an ISO standard. It probably won't but it might and until it's
published it is Not "in the standard"

 

[Harald van Dijk]

He is quoting from N869.txt

No, he's not. He didn't quote anything other than jacob navia's message.

And as far as I can find, N869.txt does not contain any mention of
#pragma once anyway.

 

[jameskuyper]

He is quoting from N869.txt

I didn't see any quotations about "#pragma once", and it's certainly
not present in my copy of n869.pdf.

 

[Al Balmer]

He is quoting from N869.txt


However you have to bare in mind that an N document is NOT an ISO
standard and the contents of an N document could change completely en
route to an ISO standard. It probably won't but it might and until it's
published it is Not "in the standard"

Don't worry, "#pragma once" is not in the actual, real, official C99
standard, either.