Hello,
We are trying to compile Proton on Solaris. We have stumbled upon the usage of
macro (__attribute__) which is only available in GCC and not on SunStudio.
In proton-c/bindings/cpp/include/proton/internal/export.hpp:
# define PN_CPP_EXPORT __attribute ((visibility ("default")))
Checking GCC definition of "__attribute " and "visibility", it seems that
default visibility does nothing because it is the default behavior.
Is there a reason for this definition? If not, can we safely define
PN_CPP_EXPORT and PN_CPP_CLASS_IMPORT to empty macro in that case in the
"#else" part?
https://gcc.gnu.org/onlinedocs/gcc-4.9.1/gcc/Function-Attributes.html
visibility ("visibility_type")
This attribute affects the linkage of the declaration to which it is attached.
There are four supported visibility_type values: default, hidden, protected or
internal visibility.
void __attribute__ ((visibility ("protected")))
f () { /* Do something. */; }
int i __attribute__ ((visibility ("hidden")));
The possible values of visibility_type correspond to the visibility settings in
the ELF gABI.
default
Default visibility is the normal case for the object file format. This value is
available for the visibility attribute to override other options that may
change the assumed visibility of entities.
On ELF, default visibility means that the declaration is visible to other
modules and, in shared libraries, means that the declared entity may be
overridden.
On Darwin, default visibility means that the declaration is visible to other
modules.
Default visibility corresponds to "external linkage" in the language.
Function Attributes - Using the GNU Compiler Collection
(GCC)<https://gcc.gnu.org/onlinedocs/gcc-4.9.1/gcc/Function-Attributes.html>
gcc.gnu.org
6.30 Declaring Attributes of Functions. In GNU C, you declare certain things
about functions called in your program which help the compiler optimize
function calls ...
Regards,
Adel
