Remove false warning of missing libpthread.so on Linux

Issue #477 (bdwgc).

Some libc implementations like bionic, uclib and glibc 2.34 (and later)
do not have libpthread.so because the pthreads-related code is located
in libc.so, thus potential calloc calls from such code are forwarded
to real (libc) calloc without any special handling on the libgc side.

* malloc.c [REDIRECT_MALLOC && !REDIRECT_MALLOC_IN_HEADER
&& GC_LINUX_THREADS] (GC_init_lib_bounds): Do not call WARN to report
missing libpthread.so if __UCLIBC__ or not defined __GLIBC__ or glibc
version is 2.34 or above; add comment and TODO item.

1 files changed, 12 insertions, 2 deletions

diff --git a/malloc.c b/malloc.c
index be426e86..44db8423 100644
--- a/malloc.c
+++ b/malloc.c
@@ -469,9 +469,19 @@ GC_API GC_ATTR_MALLOC void * GC_CALL GC_malloc_uncollectable(size_t lb)
       GC_init(); /* if not called yet */
       if (!GC_text_mapping("libpthread-",
                            &GC_libpthread_start, &GC_libpthread_end)) {
+        /* Some libc implementations like bionic, uclib and glibc 2.34  */
+        /* do not have libpthread.so because the pthreads-related code  */
+        /* is located in libc.so, thus potential calloc calls from such */
+        /* code are forwarded to real (libc) calloc without any special */
+        /* handling on the libgc side.  Checking glibc version at       */
+        /* compile time to turn off the warning seems to be fine.       */
+        /* TODO: Remove GC_text_mapping() call for this case.           */
+#       if defined(__GLIBC__) && !defined(__UCLIBC__) \
+           && (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 34))
           WARN("Failed to find libpthread.so text mapping: Expect crash\n", 0);
-          /* This might still work with some versions of libpthread,      */
-          /* so we don't abort.  Perhaps we should.                       */
+          /* This might still work with some versions of libpthread,    */
+          /* so we do not abort.                                        */
+#       endif
       }
       if (!GC_text_mapping("ld-", &GC_libld_start, &GC_libld_end)) {
           WARN("Failed to find ld.so text mapping: Expect crash\n", 0);