Why is gcc not showing a warning message for using $ in a variable name?
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I'm new to C and am learning C from Programming in C, 4th ed. by Stephen Kochan. On page 29, he writes $ is not a valid character for variable names. He is using the C11 standard.
I wrote the following code
#include <stdio.h>
int main (void)
{
int a$ = 1;
printf ("%i", a$);
return 0;
}
and ran it with the command gcc -std=c11 -pedantic practice.c -o practice.o && ./practice.o. My filename is practice.c.
The output is 1. Shouldn't the compiler give me a warning for using $? Isn't using $ sign for identifiers an extension that GCC provides?
I'm using GCC 8.2.0 in Ubuntu 18.10.
Edit:
Also, doesn't GCC not use the GNU extensions when I use -std=c11? That is what is written in the Appendix of the book (pg. no. 497).
I am getting an warning by using -std=c89 though.
c gcc gcc-warning
asked Mar 10 at 11:05
Apoorv PotnisApoorv Potnis
1638
|
show 6 more comments
I'm new to C and am learning C from Programming in C, 4th ed. by Stephen Kochan. On page 29, he writes $ is not a valid character for variable names. He is using the C11 standard.
I wrote the following code
#include <stdio.h>
int main (void)
{
int a$ = 1;
printf ("%i", a$);
return 0;
}
and ran it with the command gcc -std=c11 -pedantic practice.c -o practice.o && ./practice.o. My filename is practice.c.
The output is 1. Shouldn't the compiler give me a warning for using $? Isn't using $ sign for identifiers an extension that GCC provides?
I'm using GCC 8.2.0 in Ubuntu 18.10.
Edit:
Also, doesn't GCC not use the GNU extensions when I use -std=c11? That is what is written in the Appendix of the book (pg. no. 497).
I am getting an warning by using -std=c89 though.
c gcc gcc-warning
asked Mar 10 at 11:05
Apoorv PotnisApoorv Potnis
1638
8
Unrelated, but the.oextension is usually used for object files, not for the final executable.
– Federico klez Culloca
Mar 10 at 11:23
3
There's no extension for executables in *nix systems. The filesystem doesn't use that to determine the type of a file. So usually executables just don't have extensions andpracticeis correct. Check your/usr/bindirectory and you'll see that the programs there don't have an extension either.
– Federico klez Culloca
Mar 10 at 11:37
2
About the fact that its properties say "shared library" is probably because of your desktop environment. If I dofile practicefrom the command line I getpractice: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=928002f23b27d5c9bc55a15bf769edfaf3e62c23, not stripped
– Federico klez Culloca
Mar 10 at 11:40
1
Thefileutility can showshared objectfor an ELF executable if it is a position-independent executable. Some distributions configure GCC so that it creates position-independent executables by default (usually this requires using-pieand-fPICoptions).
– Sergey Vlasov
Mar 10 at 15:06
1
@MrLister: Although traditional BASIC implementations used $ as a suffix for string-variable names, I wouldn't expect a trailing $ to have similar meanings in C. If I was examining code that used such a suffix, I'd expect that the programmer was exploiting some special way that the target implementation would process identifiers with such a suffix. For example, a compiler targeting a platform which can access objects near the frame pointer faster than those which are further away might place all objects whose names have a trailing$after those that don't.
– supercat
Mar 10 at 17:41
|
show 6 more comments
I'm new to C and am learning C from Programming in C, 4th ed. by Stephen Kochan. On page 29, he writes $ is not a valid character for variable names. He is using the C11 standard.
I wrote the following code
#include <stdio.h>
int main (void)
{
int a$ = 1;
printf ("%i", a$);
return 0;
}
and ran it with the command gcc -std=c11 -pedantic practice.c -o practice.o && ./practice.o. My filename is practice.c.
The output is 1. Shouldn't the compiler give me a warning for using $? Isn't using $ sign for identifiers an extension that GCC provides?
I'm using GCC 8.2.0 in Ubuntu 18.10.
Edit:
Also, doesn't GCC not use the GNU extensions when I use -std=c11? That is what is written in the Appendix of the book (pg. no. 497).
I am getting an warning by using -std=c89 though.
c gcc gcc-warning
asked Mar 10 at 11:05
Apoorv PotnisApoorv Potnis
1638
I'm new to C and am learning C from Programming in C, 4th ed. by Stephen Kochan. On page 29, he writes $ is not a valid character for variable names. He is using the C11 standard.
I wrote the following code
#include <stdio.h>
int main (void)
{
int a$ = 1;
printf ("%i", a$);
return 0;
}
and ran it with the command gcc -std=c11 -pedantic practice.c -o practice.o && ./practice.o. My filename is practice.c.
The output is 1. Shouldn't the compiler give me a warning for using $? Isn't using $ sign for identifiers an extension that GCC provides?
I'm using GCC 8.2.0 in Ubuntu 18.10.
Edit:
Also, doesn't GCC not use the GNU extensions when I use -std=c11? That is what is written in the Appendix of the book (pg. no. 497).
I am getting an warning by using -std=c89 though.
c gcc gcc-warning
c gcc gcc-warning
asked Mar 10 at 11:05
Apoorv PotnisApoorv Potnis
1638
asked Mar 10 at 11:05
Apoorv PotnisApoorv Potnis
1638
edited Mar 10 at 11:52
Apoorv Potnis
asked Mar 10 at 11:05
Apoorv PotnisApoorv Potnis
1638
asked Mar 10 at 11:05
Apoorv PotnisApoorv Potnis
1638
asked Mar 10 at 11:05
Apoorv PotnisApoorv Potnis
1638
1638
8
Unrelated, but the.oextension is usually used for object files, not for the final executable.
– Federico klez Culloca
Mar 10 at 11:23
3
There's no extension for executables in *nix systems. The filesystem doesn't use that to determine the type of a file. So usually executables just don't have extensions andpracticeis correct. Check your/usr/bindirectory and you'll see that the programs there don't have an extension either.
– Federico klez Culloca
Mar 10 at 11:37
2
About the fact that its properties say "shared library" is probably because of your desktop environment. If I dofile practicefrom the command line I getpractice: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=928002f23b27d5c9bc55a15bf769edfaf3e62c23, not stripped
– Federico klez Culloca
Mar 10 at 11:40
1
Thefileutility can showshared objectfor an ELF executable if it is a position-independent executable. Some distributions configure GCC so that it creates position-independent executables by default (usually this requires using-pieand-fPICoptions).
– Sergey Vlasov
Mar 10 at 15:06
1
@MrLister: Although traditional BASIC implementations used $ as a suffix for string-variable names, I wouldn't expect a trailing $ to have similar meanings in C. If I was examining code that used such a suffix, I'd expect that the programmer was exploiting some special way that the target implementation would process identifiers with such a suffix. For example, a compiler targeting a platform which can access objects near the frame pointer faster than those which are further away might place all objects whose names have a trailing$after those that don't.
– supercat
Mar 10 at 17:41
|
show 6 more comments
8
Unrelated, but the.oextension is usually used for object files, not for the final executable.
– Federico klez Culloca
Mar 10 at 11:23
3
There's no extension for executables in *nix systems. The filesystem doesn't use that to determine the type of a file. So usually executables just don't have extensions andpracticeis correct. Check your/usr/bindirectory and you'll see that the programs there don't have an extension either.
– Federico klez Culloca
Mar 10 at 11:37
2
About the fact that its properties say "shared library" is probably because of your desktop environment. If I dofile practicefrom the command line I getpractice: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=928002f23b27d5c9bc55a15bf769edfaf3e62c23, not stripped
– Federico klez Culloca
Mar 10 at 11:40
1
Thefileutility can showshared objectfor an ELF executable if it is a position-independent executable. Some distributions configure GCC so that it creates position-independent executables by default (usually this requires using-pieand-fPICoptions).
– Sergey Vlasov
Mar 10 at 15:06
1
@MrLister: Although traditional BASIC implementations used $ as a suffix for string-variable names, I wouldn't expect a trailing $ to have similar meanings in C. If I was examining code that used such a suffix, I'd expect that the programmer was exploiting some special way that the target implementation would process identifiers with such a suffix. For example, a compiler targeting a platform which can access objects near the frame pointer faster than those which are further away might place all objects whose names have a trailing$after those that don't.
– supercat
Mar 10 at 17:41
8
8
Unrelated, but the
.o extension is usually used for object files, not for the final executable.– Federico klez Culloca
Mar 10 at 11:23
Unrelated, but the
.o extension is usually used for object files, not for the final executable.– Federico klez Culloca
Mar 10 at 11:23
3
3
There's no extension for executables in *nix systems. The filesystem doesn't use that to determine the type of a file. So usually executables just don't have extensions and
practice is correct. Check your /usr/bin directory and you'll see that the programs there don't have an extension either.– Federico klez Culloca
Mar 10 at 11:37
There's no extension for executables in *nix systems. The filesystem doesn't use that to determine the type of a file. So usually executables just don't have extensions and
practice is correct. Check your /usr/bin directory and you'll see that the programs there don't have an extension either.– Federico klez Culloca
Mar 10 at 11:37
2
2
About the fact that its properties say "shared library" is probably because of your desktop environment. If I do
file practice from the command line I get practice: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=928002f23b27d5c9bc55a15bf769edfaf3e62c23, not stripped– Federico klez Culloca
Mar 10 at 11:40
About the fact that its properties say "shared library" is probably because of your desktop environment. If I do
file practice from the command line I get practice: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=928002f23b27d5c9bc55a15bf769edfaf3e62c23, not stripped– Federico klez Culloca
Mar 10 at 11:40
1
1
The
file utility can show shared object for an ELF executable if it is a position-independent executable. Some distributions configure GCC so that it creates position-independent executables by default (usually this requires using -pie and -fPIC options).– Sergey Vlasov
Mar 10 at 15:06
The
file utility can show shared object for an ELF executable if it is a position-independent executable. Some distributions configure GCC so that it creates position-independent executables by default (usually this requires using -pie and -fPIC options).– Sergey Vlasov
Mar 10 at 15:06
1
1
@MrLister: Although traditional BASIC implementations used $ as a suffix for string-variable names, I wouldn't expect a trailing $ to have similar meanings in C. If I was examining code that used such a suffix, I'd expect that the programmer was exploiting some special way that the target implementation would process identifiers with such a suffix. For example, a compiler targeting a platform which can access objects near the frame pointer faster than those which are further away might place all objects whose names have a trailing
$ after those that don't.– supercat
Mar 10 at 17:41
@MrLister: Although traditional BASIC implementations used $ as a suffix for string-variable names, I wouldn't expect a trailing $ to have similar meanings in C. If I was examining code that used such a suffix, I'd expect that the programmer was exploiting some special way that the target implementation would process identifiers with such a suffix. For example, a compiler targeting a platform which can access objects near the frame pointer faster than those which are further away might place all objects whose names have a trailing
$ after those that don't.– supercat
Mar 10 at 17:41
|
show 6 more comments
2 Answers
2
active
oldest
votes
You get a warning with -std=c89 -pedantic. C99 and later allow other implementation-defined characters in identifiers.
answered Mar 10 at 11:20
nwellnhofnwellnhof
23.8k46085
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
Mar 10 at 11:34
add a comment |
According to this : GCC Documentation
In GNU C, you may normally use dollar signs in identifier names. This
is because many traditional C implementations allow such identifiers.
However, dollar signs in identifiers are not supported on a few target
machines, typically because the target assembler does not allow them.
So, $ is valid, but it's not a conforming way to code in C.
answered Mar 10 at 11:11
Arnaud PeraltaArnaud Peralta
1,161918
6
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
Mar 10 at 11:14
1
@Spidey with-std=c11no warning appears
– Federico klez Culloca
Mar 10 at 11:21
1
Try adding -Wall then, to show more warnings.
– Spidey
Mar 10 at 11:26
1
@Spidey nope, still no warnings.
– Federico klez Culloca
Mar 10 at 11:27
1
@Spidey: The Standard has no definition for "valid C". Its definition for a "conforming C program" encompasses any blob of text that is acceptable to at least one conforming C implementation. A source text that uses dollar signs in identifiers could not be a "strictly conforming proogram", but the authors of the Standard recognize that much C's usefulness stems from the ability to write non-portable programs that will be usefully processed by some C implementations even if not by all of them.
– supercat
Mar 10 at 17:17
add a comment |
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2 Answers
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2 Answers
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oldest
votes
You get a warning with -std=c89 -pedantic. C99 and later allow other implementation-defined characters in identifiers.
answered Mar 10 at 11:20
nwellnhofnwellnhof
23.8k46085
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
Mar 10 at 11:34
add a comment |
You get a warning with -std=c89 -pedantic. C99 and later allow other implementation-defined characters in identifiers.
answered Mar 10 at 11:20
nwellnhofnwellnhof
23.8k46085
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
Mar 10 at 11:34
add a comment |
You get a warning with -std=c89 -pedantic. C99 and later allow other implementation-defined characters in identifiers.
answered Mar 10 at 11:20
nwellnhofnwellnhof
23.8k46085
You get a warning with -std=c89 -pedantic. C99 and later allow other implementation-defined characters in identifiers.
answered Mar 10 at 11:20
nwellnhofnwellnhof
23.8k46085
edited Mar 10 at 11:41
answered Mar 10 at 11:20
nwellnhofnwellnhof
23.8k46085
answered Mar 10 at 11:20
nwellnhofnwellnhof
23.8k46085
answered Mar 10 at 11:20
nwellnhofnwellnhof
23.8k46085
23.8k46085
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
Mar 10 at 11:34
add a comment |
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
Mar 10 at 11:34
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
Mar 10 at 11:34
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
Mar 10 at 11:34
add a comment |
According to this : GCC Documentation
In GNU C, you may normally use dollar signs in identifier names. This
is because many traditional C implementations allow such identifiers.
However, dollar signs in identifiers are not supported on a few target
machines, typically because the target assembler does not allow them.
So, $ is valid, but it's not a conforming way to code in C.
answered Mar 10 at 11:11
Arnaud PeraltaArnaud Peralta
1,161918
6
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
Mar 10 at 11:14
1
@Spidey with-std=c11no warning appears
– Federico klez Culloca
Mar 10 at 11:21
1
Try adding -Wall then, to show more warnings.
– Spidey
Mar 10 at 11:26
1
@Spidey nope, still no warnings.
– Federico klez Culloca
Mar 10 at 11:27
1
@Spidey: The Standard has no definition for "valid C". Its definition for a "conforming C program" encompasses any blob of text that is acceptable to at least one conforming C implementation. A source text that uses dollar signs in identifiers could not be a "strictly conforming proogram", but the authors of the Standard recognize that much C's usefulness stems from the ability to write non-portable programs that will be usefully processed by some C implementations even if not by all of them.
– supercat
Mar 10 at 17:17
add a comment |
According to this : GCC Documentation
In GNU C, you may normally use dollar signs in identifier names. This
is because many traditional C implementations allow such identifiers.
However, dollar signs in identifiers are not supported on a few target
machines, typically because the target assembler does not allow them.
So, $ is valid, but it's not a conforming way to code in C.
answered Mar 10 at 11:11
Arnaud PeraltaArnaud Peralta
1,161918
6
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
Mar 10 at 11:14
1
@Spidey with-std=c11no warning appears
– Federico klez Culloca
Mar 10 at 11:21
1
Try adding -Wall then, to show more warnings.
– Spidey
Mar 10 at 11:26
1
@Spidey nope, still no warnings.
– Federico klez Culloca
Mar 10 at 11:27
1
@Spidey: The Standard has no definition for "valid C". Its definition for a "conforming C program" encompasses any blob of text that is acceptable to at least one conforming C implementation. A source text that uses dollar signs in identifiers could not be a "strictly conforming proogram", but the authors of the Standard recognize that much C's usefulness stems from the ability to write non-portable programs that will be usefully processed by some C implementations even if not by all of them.
– supercat
Mar 10 at 17:17
add a comment |
According to this : GCC Documentation
In GNU C, you may normally use dollar signs in identifier names. This
is because many traditional C implementations allow such identifiers.
However, dollar signs in identifiers are not supported on a few target
machines, typically because the target assembler does not allow them.
So, $ is valid, but it's not a conforming way to code in C.
answered Mar 10 at 11:11
Arnaud PeraltaArnaud Peralta
1,161918
According to this : GCC Documentation
In GNU C, you may normally use dollar signs in identifier names. This
is because many traditional C implementations allow such identifiers.
However, dollar signs in identifiers are not supported on a few target
machines, typically because the target assembler does not allow them.
So, $ is valid, but it's not a conforming way to code in C.
answered Mar 10 at 11:11
Arnaud PeraltaArnaud Peralta
1,161918
edited Mar 10 at 21:13
answered Mar 10 at 11:11
Arnaud PeraltaArnaud Peralta
1,161918
answered Mar 10 at 11:11
Arnaud PeraltaArnaud Peralta
1,161918
answered Mar 10 at 11:11
Arnaud PeraltaArnaud Peralta
1,161918
1,161918
6
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
Mar 10 at 11:14
1
@Spidey with-std=c11no warning appears
– Federico klez Culloca
Mar 10 at 11:21
1
Try adding -Wall then, to show more warnings.
– Spidey
Mar 10 at 11:26
1
@Spidey nope, still no warnings.
– Federico klez Culloca
Mar 10 at 11:27
1
@Spidey: The Standard has no definition for "valid C". Its definition for a "conforming C program" encompasses any blob of text that is acceptable to at least one conforming C implementation. A source text that uses dollar signs in identifiers could not be a "strictly conforming proogram", but the authors of the Standard recognize that much C's usefulness stems from the ability to write non-portable programs that will be usefully processed by some C implementations even if not by all of them.
– supercat
Mar 10 at 17:17
add a comment |
6
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
Mar 10 at 11:14
1
@Spidey with-std=c11no warning appears
– Federico klez Culloca
Mar 10 at 11:21
1
Try adding -Wall then, to show more warnings.
– Spidey
Mar 10 at 11:26
1
@Spidey nope, still no warnings.
– Federico klez Culloca
Mar 10 at 11:27
1
@Spidey: The Standard has no definition for "valid C". Its definition for a "conforming C program" encompasses any blob of text that is acceptable to at least one conforming C implementation. A source text that uses dollar signs in identifiers could not be a "strictly conforming proogram", but the authors of the Standard recognize that much C's usefulness stems from the ability to write non-portable programs that will be usefully processed by some C implementations even if not by all of them.
– supercat
Mar 10 at 17:17
6
6
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
Mar 10 at 11:14
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
Mar 10 at 11:14
1
1
@Spidey with
-std=c11 no warning appears– Federico klez Culloca
Mar 10 at 11:21
@Spidey with
-std=c11 no warning appears– Federico klez Culloca
Mar 10 at 11:21
1
1
Try adding -Wall then, to show more warnings.
– Spidey
Mar 10 at 11:26
Try adding -Wall then, to show more warnings.
– Spidey
Mar 10 at 11:26
1
1
@Spidey nope, still no warnings.
– Federico klez Culloca
Mar 10 at 11:27
@Spidey nope, still no warnings.
– Federico klez Culloca
Mar 10 at 11:27
1
1
@Spidey: The Standard has no definition for "valid C". Its definition for a "conforming C program" encompasses any blob of text that is acceptable to at least one conforming C implementation. A source text that uses dollar signs in identifiers could not be a "strictly conforming proogram", but the authors of the Standard recognize that much C's usefulness stems from the ability to write non-portable programs that will be usefully processed by some C implementations even if not by all of them.
– supercat
Mar 10 at 17:17
@Spidey: The Standard has no definition for "valid C". Its definition for a "conforming C program" encompasses any blob of text that is acceptable to at least one conforming C implementation. A source text that uses dollar signs in identifiers could not be a "strictly conforming proogram", but the authors of the Standard recognize that much C's usefulness stems from the ability to write non-portable programs that will be usefully processed by some C implementations even if not by all of them.
– supercat
Mar 10 at 17:17
add a comment |
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8
Unrelated, but the
.oextension is usually used for object files, not for the final executable.– Federico klez Culloca
Mar 10 at 11:23
3
There's no extension for executables in *nix systems. The filesystem doesn't use that to determine the type of a file. So usually executables just don't have extensions and
practiceis correct. Check your/usr/bindirectory and you'll see that the programs there don't have an extension either.– Federico klez Culloca
Mar 10 at 11:37
2
About the fact that its properties say "shared library" is probably because of your desktop environment. If I do
file practicefrom the command line I getpractice: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=928002f23b27d5c9bc55a15bf769edfaf3e62c23, not stripped– Federico klez Culloca
Mar 10 at 11:40
1
The
fileutility can showshared objectfor an ELF executable if it is a position-independent executable. Some distributions configure GCC so that it creates position-independent executables by default (usually this requires using-pieand-fPICoptions).– Sergey Vlasov
Mar 10 at 15:06
1
@MrLister: Although traditional BASIC implementations used $ as a suffix for string-variable names, I wouldn't expect a trailing $ to have similar meanings in C. If I was examining code that used such a suffix, I'd expect that the programmer was exploiting some special way that the target implementation would process identifiers with such a suffix. For example, a compiler targeting a platform which can access objects near the frame pointer faster than those which are further away might place all objects whose names have a trailing
$after those that don't.– supercat
Mar 10 at 17:41