syntax error in switch statement

[Guybrush Threepwood]

This is a simplified example of a problem I'm having:

typedef struct node {
int a;
int b;
} NODE;

Somewhere in my code following lines can be found:

switch(op) {
case someLabel:
NODE *n = node(1, 2);
break;
default:
break;
}

Now when I compile this code with gcc version 3.4.6, I get an error:
error: syntax error before '*' token
error: `n' undeclared (first use in this function)
error: (Each undeclared identifier is reported only once
error: for each function it appears in.)

This has to do with the fact the declaration of *n is the first line of
the case. If I put, for example, an fprintf before the declaration, the
code compiles fine.

--
"Don't worry about people stealing your ideas. If your ideas are any
good, you'll have to ram them down people's throats."
-- Howard Aiken

[Eric Sosman]

Guybrush Threepwood wrote:

This is a simplified example of a problem I'm having:

typedef struct node {
int a;
int b;
} NODE;

Somewhere in my code following lines can be found:

switch(op) {
case someLabel:
NODE *n = node(1, 2);
break;
default:
break;
}

Now when I compile this code with gcc version 3.4.6, I get an error:
error: syntax error before '*' token
error: `n' undeclared (first use in this function)
error: (Each undeclared identifier is reported only once
error: for each function it appears in.)

This has to do with the fact the declaration of *n is the first line of
the case. If I put, for example, an fprintf before the declaration, the
code compiles fine.

A label must be followed by a statement. A declaration
is not a statement. Possible fixes

case someLabel:
; /* an empty statement */
NODE *n = node(1, 2);
break;

case someLabel:
/* a compound statement: */
{
NODE *n = node(1, 2);
break;
}

--
Eric Sosman
es*****@acm-dot-org.invalid

[Thad Smith]

Eric Sosman wrote:

Guybrush Threepwood wrote:

>This is a simplified example of a problem I'm having:

typedef struct node {
int a;
int b;
} NODE;

Somewhere in my code following lines can be found:

switch(op) {
case someLabel:
NODE *n = node(1, 2);
break;
default:
break;
}

A label must be followed by a statement. A declaration
is not a statement. Possible fixes

case someLabel:
; /* an empty statement */
NODE *n = node(1, 2);
break;

While this works for C99, its worth noting that most C compilers don't
support C99. I recommend not using this if portability to C90 compilers
is important.

--
Thad

[Richard Bos]

Thad Smith <Th*******@acm.orgwrote:

Eric Sosman wrote:

Guybrush Threepwood wrote:

This is a simplified example of a problem I'm having:

typedef struct node {
int a;
int b;
} NODE;

Somewhere in my code following lines can be found:

switch(op) {
case someLabel:
NODE *n = node(1, 2);
break;
default:
break;
}

A label must be followed by a statement. A declaration
is not a statement. Possible fixes

case someLabel:
; /* an empty statement */
NODE *n = node(1, 2);
break;

While this works for C99, its worth noting that most C compilers don't
support C99. I recommend not using this if portability to C90 compilers
is important.

Yes; a portable fix is

switch(op) {
NODE *n;
case someLabel:
n = node(1, 2);
break;
default:
break;
}

I must say I'm not sure whether I like that, but it should work.

Richard

[Ian Collins]

Richard Bos wrote:

Thad Smith <Th*******@acm.orgwrote:

>Eric Sosman wrote:

>>Guybrush Threepwood wrote:

This is a simplified example of a problem I'm having:

typedef struct node {
int a;
int b;
} NODE;

Somewhere in my code following lines can be found:

switch(op) {
case someLabel:
NODE *n = node(1, 2);
break;
default:
break;
}
A label must be followed by a statement. A declaration
is not a statement. Possible fixes

case someLabel:
; /* an empty statement */
NODE *n = node(1, 2);
break;

While this works for C99, its worth noting that most C compilers don't
support C99. I recommend not using this if portability to C90 compilers
is important.

Yes; a portable fix is

switch(op) {
NODE *n;
case someLabel:
n = node(1, 2);
break;
default:
break;
}

Or add a compound statement:

switch(op) {
case someLabel:
{
NODE* n = node(1, 2);
}
break;
default:
break;
}

Better still, call a function!

--
Ian Collins.

[Flash Gordon]

Richard Bos wrote, On 08/06/07 07:34:

Thad Smith <Th*******@acm.orgwrote:

>Eric Sosman wrote:

>>Guybrush Threepwood wrote:

This is a simplified example of a problem I'm having:

typedef struct node {
int a;
int b;
} NODE;

Somewhere in my code following lines can be found:

switch(op) {
case someLabel:
NODE *n = node(1, 2);
break;
default:
break;
}
A label must be followed by a statement. A declaration
is not a statement. Possible fixes

case someLabel:
; /* an empty statement */
NODE *n = node(1, 2);
break;

While this works for C99, its worth noting that most C compilers don't
support C99. I recommend not using this if portability to C90 compilers
is important.

Yes; a portable fix is

switch(op) {
NODE *n;
case someLabel:
n = node(1, 2);
break;
default:
break;
}

I must say I'm not sure whether I like that, but it should work.

I would do
switch(op) {
case someLabel:
{
NODE *n = node(1, 2);
break;
}
default:
break;
}

Of course, it only makes sense if there is more code in that case making
use of n.
--
Flash Gordon

[Richard Tobin]

In article <46*****************@news.xs4all.nl>,
Richard Bos <rl*@hoekstra-uitgeverij.nlwrote:

>Yes; a portable fix is

switch(op) {
NODE *n;
case someLabel:
n = node(1, 2);
break;
default:
break;
}

I must say I'm not sure whether I like that, but it should work.

I see no strong reason to object to it, but bear in mind that it won't
work to use an initialiser.

-- Richard
--
"Consideration shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.

[Guybrush Threepwood]

On Fri, 08 Jun 2007 19:10:10 +1200, Ian Collins wrote:

Richard Bos wrote:

>Thad Smith <Th*******@acm.orgwrote:

>>Eric Sosman wrote:
Guybrush Threepwood wrote:
A label must be followed by a statement. A declaration
is not a statement. Possible fixes

case someLabel:
; /* an empty statement */
NODE *n = node(1, 2);
break;
While this works for C99, its worth noting that most C compilers don't
support C99. I recommend not using this if portability to C90 compilers
is important.

Yes; a portable fix is

switch(op) {
NODE *n;
case someLabel:
n = node(1, 2);
break;
default:
break;
}

Or add a compound statement:

switch(op) {
case someLabel:
{
NODE* n = node(1, 2);
}
break;
default:
break;
}

Better still, call a function!

Ok, thanks for the replies everyone.

--
"Don't worry about people stealing your ideas. If your ideas are any
good, you'll have to ram them down people's throats."
-- Howard Aiken

[Christopher Benson-Manica]

Richard Bos <rl*@hoekstra-uitgeverij.nlwrote:

switch(op) {
NODE *n;
case someLabel:
n = node(1, 2);
break;
default:
break;
}

I must say I'm not sure whether I like that, but it should work.

My personal opinion is that it may induce a sleepy programmer to
attempt to use an uninitialized n in one of the switch cases. It's
not quite at the level of handing the maintainer a gun for his foot,
but placing a "SHOOT ME" sign on a foot is still a bad idea :-)

--
C. Benson Manica | I *should* know what I'm talking about - if I
cbmanica(at)gmail.com | don't, I need to know. Flames welcome.