On 19 February 2011 13:40, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote:
> On 19 February 2011 13:40, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote:
>> On 19 February 2011 09:41, Graham Bloice wrote:
>>> I'm getting problems with g++ compiling some headers:
>>>
>>> #ifdef __cplusplus
>>> extern "C" {
>>> #endif
>>>
>>> typedef enum abc xyz;
>>> enum abc {
>>> p1 = 0,
>>> p2,
>>> p3
>>> };
>>>
>>> #ifdef __cplusplus
>>> }
>>> #endif
>>>
>>> This code compiles with the mbed cloud compiler, Keil RV and VS2010,
>>> but not g++ 4.4.5. The errors are:
>>>
>>> test.cpp:5: error: use of enum ‘abc’ without previous declaration
>>> test.cpp:5: error: invalid type in declaration before ‘;’ token
>>>
>>> From a previous query I understand that the code isn't legal c++, but
>>> is legal c, as demonstrated when I compile the code using the -x c
>>> option.
>>>
>>> I'm guessing here, but do some compilers switch into a C compilation
>>> mode when they hit an extern "C"? I know extern "C" affects the
>>> linkage but is it meant to affect compilation mode?
>>
>> G++ doesn't, and a conforming compiler shouldn't - but this is the
>> wrong place to ask about "somt compilers".
>>
>> For a conforming compiler extern "C" only tells the C++ compiler to
>> use different linkage for the enclosed functions. It absolutely does
>> not cause it to compile as C, as can be shown by the fact that C++
>> features are allowed inside extern "C" blocks:
>>
>> #include <string>
>> extern "C" void f() { throw std::runtime_error("I am C++"); }
>>
>
> Oops, I should have included <stdexcept>, I changed the example and
> didn't correct the header.
>
Thanks for that. I'll have a moan at the vendor to correct their
headers to be compliant by putting the typdef after the enum.
--
Regards,
Graham Bloice
