[CMake] several questions about cmake

[Michael Hertling]

On 08/26/2010 05:38 PM, Mark Roden wrote:

>>> 2) I'm trying to check to see if a certain C++ code chunk will
>>> compile.  The line is:
>>>
>>> CHECK_CXX_SOURCE_COMPILES("
>>> #include <string.h>
>>> #include <stdio.h>
>>> void main(){
>>>  char buf[100];
>>>  char buf2[100];
>>>  strncpy(buf2, buf, 5);
>>>  buf2[5] = '\0';
>>>  puts(buf2);
>>> }" EXTERN_C)
>>>
>>> The EXTERN_C test is failing here.  The problem is, I can cut and
>>> paste that code into a blank project in vs2008 and it compiles just
>>> fine.  Is there a way to see the compiler error, or to determine why
>>> that would fail?
>>>
>>> The code in the configure.in file is:
>>>
>>> AC_TRY_LINK([
>>> # include <string.h>
>>> # include <stdio.h>
>>> ], [
>>>  char buf[100];
>>>  strcpy(buf, "Hello world\n");
>>> ],
>>>  bz_cv_cplusplus_needexternCwrapper=no,
>>>  bz_cv_cplusplus_needexternCwrapper=yes)
>>> ])
>>>
>>> I can't use that directly (or can I?) because the quotation marks in
>>> "Hello World" prematurely cut off the code in the SOURCE section of
>>> CHECK_CXX_SOURCE_COMPILES, and I get an error that the variable World"
>>> makes no sense.
>>
>> Just put \ in front of the quotation marks, and the hello world code will work.
> 
> That's not my point.  The code I gave has no double quotes in it, and
> it still doesn't compile properly, but it does compile and work in a
> visual studio environment.
> If I do:
> 
> CHECK_CXX_SOURCE_COMPILES("
> #include <string.h>
> #include <stdio.h>
>  void main(){
>   char buf[100];
>   strcpy(buf, \"Hello world\n\");
>  }" EXTERN_C)
> 
> I get
> 
> Performing Test EXTERN_C
> Performing Test EXTERN_C - Failed
> 
> But that code compiles in an empty vs2008 project.
> 
>  How can I get the compiler error?  I don't see why this code test should fail.

You need to escape the newline in the string literal four-fold, i.e.
\"Hello world\\\\n\". Moreover, "void" isn't allowed as the return
type of main() in C++, use "int" instead.

Regards,

Michael