Re: libtool problem on FreeBSD 4.1 with -pthread

[Bob Friesenhahn]

On Mon, 8 Nov 2004, Ralf Wildenhues wrote:
> > A build system for a program that uses threads should compile _every_ _source_
> > _file_ with platform-appropriate CPPFLAGS (e.g. -D_REENTRANT -D_THREAD_SAFE).
>
> This is what the whole question boils down to.  Even if the main program
> does not use threads (only a shared lib it uses), is it necessary for it
> to be compiled with those flags (as opposed to only be linked with)?

Usually.  Linux seems to incorporate thread-safe errno and other 
features in single-threaded programs.  Other operating systems may 
encounter situations where a thread-safe library uses thread-specific 
errno wrapper functions while the program and other libraries use a 
static global errno variable, leading to potentially improper 
behavior.  Interfaces like stdio usually require special compilation 
since they rely on macros or may even change their binary interface. 
Under Solaris, many functions used to support thread-safety use "weak" 
linkage so if the pthread library is not supplied, the application 
runs with dummy versions which do nothing.

> What we could do now, however, is complain if a library uses threads and
> the other program sources weren't compiled with the thread-safe flag.  Not
> too brilliant, but better than nothing if at the end of your build it
> says

Sounds great, but it would incur the wrath of many.  Violations of 
thread-safe principles are rampant.

Bob
======================================
Bob Friesenhahn
address@hidden
http://www.simplesystems.org/users/bfriesen