Why is gcc not showing a warning message for using $ in a variable name?
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 1 hour ago
Apoorv PotnisApoorv Potnis
1336
New contributor
Apoorv Potnis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
|
show 2 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 1 hour ago
Apoorv PotnisApoorv Potnis
1336
New contributor
Apoorv Potnis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
It is valid, but not recommended, for readability sake...
– Matthieu
1 hour ago
3
Unrelated, but the.oextension is usually used for object files, not for the final executable.
– Federico klez Culloca
1 hour ago
@FedericoklezCulloca Can I ask what is the extension of the final executable? When I remove.othe file still gets compiled. There is a file namedpracticein my directory. What is its extension? Its properties show type as "shared library".
– Apoorv Potnis
53 mins ago
2
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
47 mins ago
1
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
45 mins ago
|
show 2 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 1 hour ago
Apoorv PotnisApoorv Potnis
1336
New contributor
Apoorv Potnis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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 1 hour ago
Apoorv PotnisApoorv Potnis
1336
New contributor
Apoorv Potnis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 1 hour ago
Apoorv PotnisApoorv Potnis
1336
New contributor
Apoorv Potnis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 32 mins ago
Apoorv Potnis
asked 1 hour ago
Apoorv PotnisApoorv Potnis
1336
New contributor
Apoorv Potnis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 1 hour ago
Apoorv PotnisApoorv Potnis
1336
asked 1 hour ago
Apoorv PotnisApoorv Potnis
1336
1336
New contributor
Apoorv Potnis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Apoorv Potnis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Apoorv Potnis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
It is valid, but not recommended, for readability sake...
– Matthieu
1 hour ago
3
Unrelated, but the.oextension is usually used for object files, not for the final executable.
– Federico klez Culloca
1 hour ago
@FedericoklezCulloca Can I ask what is the extension of the final executable? When I remove.othe file still gets compiled. There is a file namedpracticein my directory. What is its extension? Its properties show type as "shared library".
– Apoorv Potnis
53 mins ago
2
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
47 mins ago
1
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
45 mins ago
|
show 2 more comments
It is valid, but not recommended, for readability sake...
– Matthieu
1 hour ago
3
Unrelated, but the.oextension is usually used for object files, not for the final executable.
– Federico klez Culloca
1 hour ago
@FedericoklezCulloca Can I ask what is the extension of the final executable? When I remove.othe file still gets compiled. There is a file namedpracticein my directory. What is its extension? Its properties show type as "shared library".
– Apoorv Potnis
53 mins ago
2
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
47 mins ago
1
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
45 mins ago
It is valid, but not recommended, for readability sake...
– Matthieu
1 hour ago
It is valid, but not recommended, for readability sake...
– Matthieu
1 hour ago
3
3
Unrelated, but the
.o extension is usually used for object files, not for the final executable.– Federico klez Culloca
1 hour ago
Unrelated, but the
.o extension is usually used for object files, not for the final executable.– Federico klez Culloca
1 hour ago
@FedericoklezCulloca Can I ask what is the extension of the final executable? When I remove
.o the file still gets compiled. There is a file named practice in my directory. What is its extension? Its properties show type as "shared library".– Apoorv Potnis
53 mins ago
@FedericoklezCulloca Can I ask what is the extension of the final executable? When I remove
.o the file still gets compiled. There is a file named practice in my directory. What is its extension? Its properties show type as "shared library".– Apoorv Potnis
53 mins ago
2
2
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
47 mins ago
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
47 mins ago
1
1
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
45 mins ago
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
45 mins ago
|
show 2 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 1 hour ago
nwellnhofnwellnhof
23.6k46084
Was editing just when you answered.
– Apoorv Potnis
1 hour ago
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
51 mins ago
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. I don't know why your book says the opposite.
edited 1 hour ago
Federico klez Culloca
16k134380
answered 1 hour ago
Arnaud PeraltaArnaud Peralta
610116
2
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
1 hour ago
@Spidey with-std=c11no warning appears
– Federico klez Culloca
1 hour ago
1
Try adding -Wall then, to show more warnings.
– Spidey
59 mins ago
@Spidey nope, still no warnings.
– Federico klez Culloca
57 mins ago
add a comment |
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2 Answers
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2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
You get a warning with -std=c89 -pedantic. C99 and later allow other implementation-defined characters in identifiers.
answered 1 hour ago
nwellnhofnwellnhof
23.6k46084
Was editing just when you answered.
– Apoorv Potnis
1 hour ago
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
51 mins ago
add a comment |
You get a warning with -std=c89 -pedantic. C99 and later allow other implementation-defined characters in identifiers.
answered 1 hour ago
nwellnhofnwellnhof
23.6k46084
Was editing just when you answered.
– Apoorv Potnis
1 hour ago
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
51 mins ago
add a comment |
You get a warning with -std=c89 -pedantic. C99 and later allow other implementation-defined characters in identifiers.
answered 1 hour ago
nwellnhofnwellnhof
23.6k46084
You get a warning with -std=c89 -pedantic. C99 and later allow other implementation-defined characters in identifiers.
answered 1 hour ago
nwellnhofnwellnhof
23.6k46084
edited 43 mins ago
answered 1 hour ago
nwellnhofnwellnhof
23.6k46084
answered 1 hour ago
nwellnhofnwellnhof
23.6k46084
answered 1 hour ago
nwellnhofnwellnhof
23.6k46084
23.6k46084
Was editing just when you answered.
– Apoorv Potnis
1 hour ago
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
51 mins ago
add a comment |
Was editing just when you answered.
– Apoorv Potnis
1 hour ago
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
51 mins ago
Was editing just when you answered.
– Apoorv Potnis
1 hour ago
Was editing just when you answered.
– Apoorv Potnis
1 hour ago
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
51 mins ago
Yes. This is the reference: gcc.gnu.org/onlinedocs/gcc-8.2.0/cpp/…
– Apoorv Potnis
51 mins ago
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. I don't know why your book says the opposite.
edited 1 hour ago
Federico klez Culloca
16k134380
answered 1 hour ago
Arnaud PeraltaArnaud Peralta
610116
2
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
1 hour ago
@Spidey with-std=c11no warning appears
– Federico klez Culloca
1 hour ago
1
Try adding -Wall then, to show more warnings.
– Spidey
59 mins ago
@Spidey nope, still no warnings.
– Federico klez Culloca
57 mins ago
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. I don't know why your book says the opposite.
edited 1 hour ago
Federico klez Culloca
16k134380
answered 1 hour ago
Arnaud PeraltaArnaud Peralta
610116
2
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
1 hour ago
@Spidey with-std=c11no warning appears
– Federico klez Culloca
1 hour ago
1
Try adding -Wall then, to show more warnings.
– Spidey
59 mins ago
@Spidey nope, still no warnings.
– Federico klez Culloca
57 mins ago
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. I don't know why your book says the opposite.
edited 1 hour ago
Federico klez Culloca
16k134380
answered 1 hour ago
Arnaud PeraltaArnaud Peralta
610116
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. I don't know why your book says the opposite.
edited 1 hour ago
Federico klez Culloca
16k134380
answered 1 hour ago
Arnaud PeraltaArnaud Peralta
610116
edited 1 hour ago
Federico klez Culloca
16k134380
edited 1 hour ago
Federico klez Culloca
16k134380
edited 1 hour ago
Federico klez Culloca
16k134380
16k134380
answered 1 hour ago
Arnaud PeraltaArnaud Peralta
610116
answered 1 hour ago
Arnaud PeraltaArnaud Peralta
610116
answered 1 hour ago
Arnaud PeraltaArnaud Peralta
610116
610116
2
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
1 hour ago
@Spidey with-std=c11no warning appears
– Federico klez Culloca
1 hour ago
1
Try adding -Wall then, to show more warnings.
– Spidey
59 mins ago
@Spidey nope, still no warnings.
– Federico klez Culloca
57 mins ago
add a comment |
2
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
1 hour ago
@Spidey with-std=c11no warning appears
– Federico klez Culloca
1 hour ago
1
Try adding -Wall then, to show more warnings.
– Spidey
59 mins ago
@Spidey nope, still no warnings.
– Federico klez Culloca
57 mins ago
2
2
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
1 hour ago
It's not valid C, only on GCC C. Try compiling with -ansi or -std=C11 and the warnings will start appearing.
– Spidey
1 hour ago
@Spidey with
-std=c11 no warning appears– Federico klez Culloca
1 hour ago
@Spidey with
-std=c11 no warning appears– Federico klez Culloca
1 hour ago
1
1
Try adding -Wall then, to show more warnings.
– Spidey
59 mins ago
Try adding -Wall then, to show more warnings.
– Spidey
59 mins ago
@Spidey nope, still no warnings.
– Federico klez Culloca
57 mins ago
@Spidey nope, still no warnings.
– Federico klez Culloca
57 mins ago
add a comment |
Apoorv Potnis is a new contributor. Be nice, and check out our Code of Conduct.
Apoorv Potnis is a new contributor. Be nice, and check out our Code of Conduct.
Apoorv Potnis is a new contributor. Be nice, and check out our Code of Conduct.
Apoorv Potnis is a new contributor. Be nice, and check out our Code of Conduct.
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It is valid, but not recommended, for readability sake...
– Matthieu
1 hour ago
3
Unrelated, but the
.oextension is usually used for object files, not for the final executable.– Federico klez Culloca
1 hour ago
@FedericoklezCulloca Can I ask what is the extension of the final executable? When I remove
.othe file still gets compiled. There is a file namedpracticein my directory. What is its extension? Its properties show type as "shared library".– Apoorv Potnis
53 mins ago
2
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
47 mins ago
1
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
45 mins ago