runtime_loader: treat weak symbols as strong symbols definitions.

http://www.sourceware.org/ml/libc-hacker/2000-06/msg00029.html
Change-Id: I15bf1f48dda32942e2a93610d62dabe0cabdc9a1
Reviewed-on: https://review.haiku-os.org/c/1191
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>

src/system/runtime_loader/elf_symbol_lookup.cpp

@@ -377,15 +377,8 @@ find_undefined_symbol_global(image_t* rootImage, image_t* image,
 					&& (otherImage->flags
 						& (RTLD_GLOBAL | RFLAG_USE_FOR_RESOLVING)) != 0)) {
 			if (elf_sym* symbol = find_symbol(otherImage, lookupInfo)) {
-				if (symbol->Bind() != STB_WEAK) {
-					*_foundInImage = otherImage;
-					return symbol;
-				}
-
-				if (candidateSymbol == NULL) {
-					candidateSymbol = symbol;
-					candidateImage = otherImage;
-				}
+				*_foundInImage = otherImage;
+				return symbol;
 			}
 		}
 		otherImage = otherImage->next;

src/tests/system/runtime_loader/test_suite/load_resolve_weak1

@@ -0,0 +1,46 @@
+#!/bin/sh
+
+# program
+# <- liba.so
+#
+# Expected: Weak symbol in liba.so resolves to symbol in program,
+# not to symbol in liba.so.
+
+
+. ./test_setup
+
+
+# create liba.so
+cat > liba.c << EOI
+int __attribute__((weak)) c() { return 2; }
+int __attribute__((weak)) a() { return c(); }
+int (*a_p)() = &c;
+int b() { return (*a_p)(); }
+EOI
+
+# build
+compile_lib -o liba.so liba.c
+
+# create program
+cat > program.c << EOI
+extern int a();
+extern int b();
+
+int c()
+{
+	return 4;
+}
+
+int
+main()
+{
+	return a() + b();
+}
+EOI
+
+# build
+compile_program -o program program.c ./liba.so
+
+# run
+test_run_ok ./program 8
+

src/tests/system/runtime_loader/test_suite/load_resolve_weak2

@@ -0,0 +1,48 @@
+#!/bin/sh
+
+# program
+# <- liba.so
+#   <- libb.so
+# <- libb.so
+# Expected: symbol in program resolves to weak alias in liba.so,
+# not to symbol in libb.so.
+
+
+. ./test_setup
+
+
+# create libb.so
+cat > libb.c << EOI
+int a() { return 4; }
+EOI
+
+# build
+compile_lib -o libb.so libb.c
+
+
+# create liba.so
+cat > liba.c << EOI
+int __a() { return 2; }
+int a() __attribute__((weak, alias("__a")));
+EOI
+
+# build
+compile_lib -o liba.so liba.c ./libb.so
+
+# create program
+cat > program.c << EOI
+extern int a();
+
+int
+main()
+{
+	return a();
+}
+EOI
+
+# build
+compile_program -o program program.c ./liba.so ./libb.so
+
+# run
+test_run_ok ./program 2
+