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[Bug libc/1814] New: dlopen/dlsym clear dlerror flag


I've come across a minor incompatibility between Linux and FreeBSD. The question
is about dlopen/dlsym calls: in case of success, should they clear the previous
dlerror() string (if it has been set) or not? Here's a sample code:

#include <stdlib.h>
#include <stdio.h>
#include <dlfcn.h>

int main(void)
{
    void *handle;
    char *error;
    double (*cosine)(double);

    handle = dlopen("/usr/lib/libm123.so", RTLD_LAZY);
    handle = dlopen("/usr/lib/libm.so", RTLD_LAZY);
    if ((error = dlerror()) != NULL) {
        fprintf(stderr, "%s\n", error);
    }

    *(void **) (&cosine) = dlsym(handle, "cos123");
    *(void **) (&cosine) = dlsym(handle, "cos");
    if ((error = dlerror()) != NULL)  {
        fprintf (stderr, "%s\n", error);
    }
    exit(0);
}

Under Linux, this runs with no error message, while FreeBSD prints it twice. The
Linux man says:

> The function dlerror() returns a human readable string describing the
> most recent error that occurred from any of the dl routines (dlopen,
> dlsym or dlclose) since the last call to dlerror().

So it looks like nothing except dlerror() itself is allowed to clear the error flag.

-- 
           Summary: dlopen/dlsym clear dlerror flag
           Product: glibc
           Version: 2.3.5
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: fnevgeny at weizmann dot ac dot il
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=1814

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