[gcc 4.1] make use of gcc 4.1 -fvisibility option
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Key: STDCXX-1031
URL: https://issues.apache.org/jira/browse/STDCXX-1031
Project: C++ Standard Library
Issue Type: Improvement
Components: Build and Installation
Affects Versions: 4.2.1
Environment: gcc 4.1 and better on ELF targets
Reporter: Martin Sebor
Assignee: Martin Sebor
Fix For: 4.2.2
The gcc 4.1 {{[-fvisibility |
http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Code-Gen-Options.html#index-fvisibility-1636]}}
option is said to
{quote}
??...very substantially improve linking and load times of shared object
libraries, produce more optimized code, provide near-perfect API export and
prevent symbol clashes. It is *strongly* recommended that you use this in any
shared objects you distribute.??
{quote}
In order for stdcxx users to benefit as described in the gcc manual we should
make use of the {{-fvisibility=hidden}} option in conjunction with
{{[\_\_attribute\_\_((visibility("default"))) |
http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Function-Attributes.html#index-g_t_0040code_007bvisibility_007d-attribute-1830]}}
on exported interfaces as the gcc manual recommends.
Besides adding the {{-fvisibility=hidden}} option to the command line when
building shared libraries with gcc, the implementation involves defining the
{{_RWSTD_EXPORT}} macro for gcc as follows:
{code}
#define _RWSTD_EXPORT __attribute__ ((visibility ("default")))
{code}
Note that since gcc requires the {{\_\_attribute\_\_}} decoration only on
function declarations and issues a warning when it appears on definitions so
the {{_RWSTD_EXPORT}} macro must not be used on definitions.
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