[tests] Regression test for EGL-glibc TLS conflict

bionic and glibc have different layouts for TLS space.
Since libEGL used a bionic slot directly (in inlined code),
libhybris's hooks didn't translate it properly and libEGL ended
up overwriting some unrelated thread-local values in glibc.

The problem only showed up when linking with libGLESv2 (which
pulls in libEGL), not when linking with libEGL directly. That's
why the test was added to test_glesv2.c

libhybris/hybris/tests/test_glesv2.c

@@ -22,6 +22,15 @@
 #include <math.h>
 #include <stddef.h>
 
+/* Regression test: make sure that there's no conflict between
+ * the TLS slots used via libEGL/bionic and the TLS space allocated
+ * by the host toolchain. The array declared here should remain zeroed
+ * regardless of GL activity. (TLS: thread-local storage)
+ * Since this array is the first __thread storage declared in the main
+ * program, glibc will allocate it before any others.
+ */
+__thread void *tls_space[64];
+
 const char vertex_src [] =
 "                                        \
    attribute vec4        position;       \
@@ -175,6 +184,18 @@ int main(int argc, char **argv)
     printf("terminated\n");
     android_dlclose(baz);
 #endif
+
+	int bad_tls = 0;
+	for (i=0; i<64; ++i) {
+		if (tls_space[i] != 0) {
+			printf("TLS array slot %d polluted: %p\n", i, tls_space[i]);
+			bad_tls++;
+		}
+	}
+	if (bad_tls)
+		return 1;
+
+	return 0;
 }
 
 // vim:ts=4:sw=4:noexpandtab