Preprocessor macro substitution

[Default User]

I've never really done too much stuff with macros. I have a program
here where an target server address is automatically generated from
WSDL. For testing, I want to use a localhost address.

I could do it by overriding the endpoint explicitly, but I'd rather
not. It would be cleaner to define a local testing environment.

My first thought was just to use a #define, like:

#define foo.bar localhost

However, that's no good as foo.bar tain't a legal identifier with that
'.' in it. Anyone have some clever preprocessor way to get what I want?





Brian

[Eric Sosman]

Re: Preprocessor macro substitution

Default User wrote:

I've never really done too much stuff with macros. I have a program
here where an target server address is automatically generated from
WSDL. For testing, I want to use a localhost address.
>
I could do it by overriding the endpoint explicitly, but I'd rather
not. It would be cleaner to define a local testing environment.
>
My first thought was just to use a #define, like:
>
#define foo.bar localhost
>
However, that's no good as foo.bar tain't a legal identifier with that
'.' in it. Anyone have some clever preprocessor way to get what I want?

What you haven't told us is where you're starting: How do
you get hold of the server address to begin with? "From WSDL"
doesn't seem to me a very complete description ...

If the C source code looks like

doSomething("fo o.bar");

.... then I think you're out of luck, unless you can muck around
with the insides of doSomething(). But if it looks like

char[] server = "foo.bar";
...
doSomething(ser ver);

.... you might be able to add `#define server "localhost" ' somewhere
between the two lines -- it's dirty, but it might work. Or if the
source looks like

#define SERVER "foo.bar"
...
doSomething(SER VER);

.... you could insert `#undef SERVER' and `#define SERVER "localhost" '
in between them -- equally dirty, just syntactically different.

But all these are one-offs, hacks, and kludges. It seems to
me that things like server addresses should usually not be hard-
compiled into programs, but should be read from an input or taken
from an environment variable or something of that sort. Would you
want to use a Web browser whose proxy settings were factory-installed
and unchangeable?

--
Eric.Sosman@sun .com

[Default User]

Re: Preprocessor macro substitution

Eric Sosman wrote:

Default User wrote:

I've never really done too much stuff with macros. I have a program
here where an target server address is automatically generated from
WSDL. For testing, I want to use a localhost address.

I could do it by overriding the endpoint explicitly, but I'd rather
not. It would be cleaner to define a local testing environment.

My first thought was just to use a #define, like:

#define foo.bar localhost

However, that's no good as foo.bar tain't a legal identifier with
that '.' in it. Anyone have some clever preprocessor way to get
what I want?

>
What you haven't told us is where you're starting: How do
you get hold of the server address to begin with? "From WSDL"
doesn't seem to me a very complete description ...

I didn't want to get too deeply into the details, but evidently I was
insufficiently thorough. The service address is specified in the WSDL.
A utility processes this and generates some C headers and source files.
Included in some places is the "endpoint" or target address. If you
don't provide an overriding address, then this is the one that is used.
So there will things like this:

if (!soap_endpoint )
soap_endpoint = "http://foo.bar:8080"

As it is generated code, I can't change that. I can provide an
endpoint, but that's fragile, as it then requires a manual update if
the WSDL is changed.

I can also do something like:

soap_endpoint = END_POINT;

Then for testing purposes:

#ifdef TESTING
#define END_POINT "http://localhost:8080"
#else
#define END_POINT NULL
#end



It's not as clean, but would work.



Brian

[Gordon Burditt]

Re: Preprocessor macro substitution

>I've never really done too much stuff with macros. I have a program

>here where an target server address is automatically generated from
>WSDL. For testing, I want to use a localhost address.

Is WSDL the double-layer version of the Weasel Server?

Host addresses are generally supplied as strings (DNS names or text
IP addresses). You could do something like:

#ifdef TEST
#define SERVER "localhost"
#else
#define SERVER "weasel.server. gov"
#endif

Then you pass SERVER to some function that looks up a name and
connects to it.

>I could do it by overriding the endpoint explicitly, but I'd rather
>not. It would be cleaner to define a local testing environment.

It is also possible with many compilers to put macro definitions
on the compiler command line and let a build script or Makefile
supply the value. I don't know whether that will help in getting
the server address from WSDL (whatever that is) to the C program.

>My first thought was just to use a #define, like:
>
>#define foo.bar localhost

A #define does not substitute something that is in double quotes.
foo.bar is unlikely to be both a valid host name and a valid
expression unless you contrived a structure declaration and variable
name to make it work.

>However, that's no good as foo.bar tain't a legal identifier with that
>'.' in it. Anyone have some clever preprocessor way to get what I want?