Reland "[libc] fix aarch64 linux full build (#95358)" (#95423)

Reverts llvm/llvm-project#95419 and Reland #95358.

This PR is full of temporal fixes. After a discussion with @lntue, it is
better to avoid further changes to the cmake infrastructure for now as a
rework to the cmake utilities will be landed in the future.

4 files changed, 32 insertions, 1 deletions

diff --git a/libc/test/IntegrationTest/CMakeLists.txt b/libc/test/IntegrationTest/CMakeLists.txt
index 4f31f10..4a99940 100644
--- a/libc/test/IntegrationTest/CMakeLists.txt
+++ b/libc/test/IntegrationTest/CMakeLists.txt
@@ -1,3 +1,7 @@
+set(arch_specific_deps)
+if(LIBC_TARGET_ARCHITECTURE_IS_AARCH64)
+  set(arch_specific_deps libc.src.sys.auxv.getauxval)
+endif()
 add_object_library(
   test
   SRCS
@@ -8,4 +12,5 @@ add_object_library(
     test.h
   DEPENDS
     libc.src.__support.OSUtil.osutil
+    ${arch_specific_deps}
 )
diff --git a/libc/test/IntegrationTest/test.cpp b/libc/test/IntegrationTest/test.cpp
index 3bdbe89..a8b2f29 100644
--- a/libc/test/IntegrationTest/test.cpp
+++ b/libc/test/IntegrationTest/test.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "src/__support/common.h"
+#include "src/sys/auxv/getauxval.h"
 #include <stddef.h>
 #include <stdint.h>
 
@@ -79,4 +81,12 @@ void *realloc(void *ptr, size_t s) {
 // Integration tests are linked with -nostdlib. BFD linker expects
 // __dso_handle when -nostdlib is used.
 void *__dso_handle = nullptr;
+
+#ifdef LIBC_TARGET_ARCH_IS_AARCH64
+// Due to historical reasons, libgcc on aarch64 may expect __getauxval to be
+// defined. See also https://gcc.gnu.org/pipermail/gcc-cvs/2020-June/300635.html
+unsigned long __getauxval(unsigned long id) {
+  return LIBC_NAMESPACE::getauxval(id);
+}
+#endif
 } // extern "C"
diff --git a/libc/test/UnitTest/CMakeLists.txt b/libc/test/UnitTest/CMakeLists.txt
index 302af30..4adc2f5 100644
--- a/libc/test/UnitTest/CMakeLists.txt
+++ b/libc/test/UnitTest/CMakeLists.txt
@@ -41,7 +41,7 @@ function(add_unittest_framework_library name)
   target_compile_options(${name}.hermetic PRIVATE ${compile_options})
 
   if(TEST_LIB_DEPENDS)
-    foreach(dep IN LISTS ${TEST_LIB_DEPENDS})
+    foreach(dep IN ITEMS ${TEST_LIB_DEPENDS})
       if(TARGET ${dep}.unit)
         add_dependencies(${name}.unit ${dep}.unit)
       else()
diff --git a/libc/test/UnitTest/HermeticTestUtils.cpp b/libc/test/UnitTest/HermeticTestUtils.cpp
index 349c182..6e815e6 100644
--- a/libc/test/UnitTest/HermeticTestUtils.cpp
+++ b/libc/test/UnitTest/HermeticTestUtils.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "src/__support/common.h"
+#include "src/sys/auxv/getauxval.h"
 #include <stddef.h>
 #include <stdint.h>
 
@@ -19,6 +21,12 @@ void *memmove(void *dst, const void *src, size_t count);
 void *memset(void *ptr, int value, size_t count);
 int atexit(void (*func)(void));
 
+// TODO: It seems that some old test frameworks does not use
+// add_libc_hermetic_test properly. Such that they won't get correct linkage
+// against the object containing this function. We create a dummy function that
+// always returns 0 to indicate a failure.
+[[gnu::weak]] unsigned long getauxval(unsigned long id) { return 0; }
+
 } // namespace LIBC_NAMESPACE
 
 namespace {
@@ -102,6 +110,14 @@ void __cxa_pure_virtual() {
 // __dso_handle when -nostdlib is used.
 void *__dso_handle = nullptr;
 
+#ifdef LIBC_TARGET_ARCH_IS_AARCH64
+// Due to historical reasons, libgcc on aarch64 may expect __getauxval to be
+// defined. See also https://gcc.gnu.org/pipermail/gcc-cvs/2020-June/300635.html
+unsigned long __getauxval(unsigned long id) {
+  return LIBC_NAMESPACE::getauxval(id);
+}
+#endif
+
 } // extern "C"
 
 void *operator new(unsigned long size, void *ptr) { return ptr; }