Fix bug in dlerror second consecutive call

According to the specs, a second consecutive call
to dlerror should always return NULL .
This was the case in dlfcn-win32 before
https://github.com/dlfcn-win32/dlfcn-win32/pull/20
introduce a regression that caused dlerror to crash
on the second consecutive call.

In this commit the issue is fixed as suggested in
https://github.com/dlfcn-win32/dlfcn-win32/issues/34
and a regression test has been added.

2 files changed, 21 insertions, 0 deletions

diff --git a/dlfcn.c b/dlfcn.c
index 4367bd7..a91e963 100644
--- a/dlfcn.c
+++ b/dlfcn.c
@@ -431,6 +431,12 @@ end:
 char *dlerror( void )

 {

     char *error_pointer = dlerror_buffer;

+    

+    /* If this is the second consecutive call to dlerror, return NULL */

+    if (current_error == NULL)

+    {

+        return NULL;

+    }

 

 #ifdef UNICODE

     errno_t err = 0;

diff --git a/test.c b/test.c
index 14523ad..ba440da 100644
--- a/test.c
+++ b/test.c
@@ -304,6 +304,21 @@ int main()
         error = dlerror( );

         printf( "SUCCESS\tCould not get nonexistent symbol from global handle: %s\n",

                 error ? error : "" );

+                

+        /* Test that the second call to dlerror() returns null as in the specs 

+           See https://github.com/dlfcn-win32/dlfcn-win32/issues/34 */

+        error = dlerror( );

+        if( error == NULL )

+        {

+            printf( "SUCCESS\tSecond consecutive call to dlerror returned NULL\n");

+        }

+        else 

+        {

+            printf( "ERROR\tSecond consecutive call to dlerror returned a non-NULL pointer: %p\n", error );

+            CLOSE_LIB;

+            CLOSE_GLOBAL;

+            RETURN_ERROR;

+        }

     }

 

     function = dlsym(global, "fwrite");