diff --git a/repos/libports/run/libc.run b/repos/libports/run/libc.run
index 4af7229bd2..a0656f0c1b 100644
--- a/repos/libports/run/libc.run
+++ b/repos/libports/run/libc.run
@@ -19,9 +19,9 @@ install_config {
 	<default-route>
 		<any-service> <parent/> <any-child/> </any-service>
 	</default-route>
-	<default caps="100"/>
+	<default caps="200"/>
 	<start name="test-libc">
-		<resource name="RAM" quantum="4M"/>
+		<resource name="RAM" quantum="400M"/>
 		<config>
 			<vfs> <dir name="dev"> <log/> </dir> </vfs>
 			<libc stdout="/dev/log"/>
@@ -35,7 +35,7 @@ build_boot_image {
 	ld.lib.so libc.lib.so libm.lib.so posix.lib.so
 }
 
-append qemu_args " -nographic -m 64 "
+append qemu_args " -nographic -m 512 "
 
 run_genode_until "child .* exited with exit value 0.*\n" 10
 
diff --git a/repos/libports/src/test/libc/main.cc b/repos/libports/src/test/libc/main.cc
index 6139408e6f..40f583a13c 100644
--- a/repos/libports/src/test/libc/main.cc
+++ b/repos/libports/src/test/libc/main.cc
@@ -1,6 +1,8 @@
 /*
  * \brief  LibC test program used during the libC porting process
  * \author Norman Feske
+ * \author Alexander Böttcher
+ * \author Christian Helmuth
  * \date   2008-10-22
  */
 
@@ -21,8 +23,8 @@
 /* libC includes */
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
-void *addr = 0;
 
 int main(int argc, char **argv)
 {
@@ -31,10 +33,89 @@ int main(int argc, char **argv)
 	printf("Does printf work?\n");
 	printf("We can find out by printing a floating-point number: %f. How does that work?\n", 1.2345);
 
-	printf("Malloc test\n");
-	addr = malloc(1234);
-	printf("Malloc returned addr = %p\n", addr);
 
-	printf("--- exit(0) from main ---\n");
-	exit(0);
+	enum { ROUNDS = 64, SIZE_LARGE = 2048 };
+
+	unsigned error_count = 0;
+
+	printf("Malloc: check small sizes\n");
+	for (size_t size = 1; size < SIZE_LARGE; size = 2*size + 3) {
+		void *addr[ROUNDS];
+		for (unsigned i = 0; i < ROUNDS; ++i) {
+			addr[i] = malloc(size);
+
+			if (!((unsigned long)addr[i] & 0xf))
+				continue;
+
+			printf("%u. malloc(%zu) returned addr = %p - ERROR\n", i, size, addr[i]);
+			++error_count;
+		}
+		for (unsigned i = 0; i < ROUNDS; ++i) free(addr[i]);
+	}
+
+	printf("Malloc: check larger sizes\n");
+	for (size_t size = SIZE_LARGE; size < 1024*1024; size = 2*size + 15) {
+		void *addr[ROUNDS];
+		for (unsigned i = 0; i < ROUNDS; ++i) {
+			addr[i] = malloc(size);
+
+			if (!((unsigned long)addr[i] & 0xf))
+				continue;
+
+			printf("%u. malloc(%zu) returned addr = %p - ERROR\n", i, size, addr[i]);
+			++error_count;
+		}
+		for (unsigned i = 0; i < ROUNDS; ++i) free(addr[i]);
+	}
+
+	printf("Malloc: check realloc\n");
+	{
+		void *addr = malloc(32);
+		memset(addr, 13, 32);
+
+		for (unsigned i = 0; i < ROUNDS; ++i) {
+			size_t const size = 32 + 11*i;
+			char *a = (char *)realloc(addr, size);
+			if (memcmp(addr, a, 32) || a[32] != 0) {
+				printf("realloc data error");
+				++error_count;
+			}
+			addr = a;
+
+			if (!((unsigned long)addr & 0xf))
+				continue;
+
+			printf("%u. realloc(%zu) returned addr = %p - ERROR\n", i, size, addr);
+			++error_count;
+		}
+		for (int i = ROUNDS - 1; i >= 0; --i) {
+			size_t const size = 32 + 11*i;
+			char *a = (char *)realloc(addr, size);
+			if (memcmp(addr, a, 32) || a[32] != 0) {
+				printf("realloc data error");
+				++error_count;
+			}
+			addr = a;
+
+			if (!((unsigned long)addr & 0xf))
+				continue;
+
+			printf("%u. realloc(%zu) returned addr = %p - ERROR\n", i, size, addr);
+			++error_count;
+		}
+	}
+
+	printf("Malloc: check really large allocation\n");
+	for (unsigned i = 0; i < 4; ++i) {
+		size_t const size = 250*1024*1024;
+		void *addr = malloc(size);
+		free(addr);
+
+		if ((unsigned long)addr & 0xf) {
+			printf("large malloc(%zu) returned addr = %p - ERROR\n", size, addr);
+			++error_count;
+		}
+	}
+
+	exit(error_count);
 }