[libcxx] [test] Fix odr_signature tests with optimizations enabled (#144317)

If optimization is enabled, the inline `f()` function actually gets
inlined, meaning that the functions `tu1()` and `tu2()` trivially return
1 and 2, instead of actually referencing the potentially linker
deduplicated function `f()`, which is what the test tries to test.

Therefore, this test previously actually failed to test what it was
supposed to test, if optimization was enabled.

Mark the inline functions with `TEST_NOINLINE` to make sure that they
don't get inlined even with optimizations enabled.

Also update the TODO comments to explain why we have an XFAIL for msvc
mode here.

This avoids these tests unexpectedly passing if building in msvc mode,
with optimizations enabled
(`-DLIBCXX_TEST_PARAMS="optimization=speed"`).

Author: mstorsjo

libcxx/test/libcxx/odr_signature.exceptions.sh.cpp

@@ -6,9 +6,11 @@
 //
 //===----------------------------------------------------------------------===//
 
-// TODO: Investigate
+// ABI tags have no effect in MSVC mode.
 // XFAIL: msvc
 
+// XFAIL: FROZEN-CXX03-HEADERS-FIXME
+
 // Test that we encode whether exceptions are supported in an ABI tag to avoid
 // ODR violations when linking TUs that have different values for it.
 
@@ -18,17 +20,19 @@
 // RUN: %{cxx} %t.tu1.o %t.tu2.o %t.main.o %{flags} %{link_flags} -o %t.exe
 // RUN: %{exec} %t.exe
 
+#include "test_macros.h"
+
 // -fno-exceptions
 #ifdef TU1
 #  include <__config>
-_LIBCPP_HIDE_FROM_ABI inline int f() { return 1; }
+_LIBCPP_HIDE_FROM_ABI TEST_NOINLINE inline int f() { return 1; }
 int tu1() { return f(); }
 #endif // TU1
 
 // -fexceptions
 #ifdef TU2
 #  include <__config>
-_LIBCPP_HIDE_FROM_ABI inline int f() { return 2; }
+_LIBCPP_HIDE_FROM_ABI TEST_NOINLINE inline int f() { return 2; }
 int tu2() { return f(); }
 #endif // TU2
 

libcxx/test/libcxx/odr_signature.hardening.sh.cpp

@@ -6,9 +6,11 @@
 //
 //===----------------------------------------------------------------------===//
 
-// TODO: Investigate
+// ABI tags have no effect in MSVC mode.
 // XFAIL: msvc
 
+// XFAIL: FROZEN-CXX03-HEADERS-FIXME
+
 // Test that we encode the hardening mode in an ABI tag to avoid ODR violations
 // when linking TUs that have different values for it.
 
@@ -21,31 +23,33 @@
 // RUN: %{cxx} %t.tu1.o %t.tu2.o %t.tu3.o %t.tu4.o %t.main.o %{flags} %{link_flags} -o %t.exe
 // RUN: %{exec} %t.exe
 
+#include "test_macros.h"
+
 // fast hardening mode
 #ifdef TU1
 #  include <__config>
-_LIBCPP_HIDE_FROM_ABI inline int f() { return 1; }
+_LIBCPP_HIDE_FROM_ABI TEST_NOINLINE inline int f() { return 1; }
 int tu1() { return f(); }
 #endif // TU1
 
 // extensive hardening mode
 #ifdef TU2
 #  include <__config>
-_LIBCPP_HIDE_FROM_ABI inline int f() { return 2; }
+_LIBCPP_HIDE_FROM_ABI TEST_NOINLINE inline int f() { return 2; }
 int tu2() { return f(); }
 #endif // TU2
 
 // debug hardening mode
 #ifdef TU3
 #  include <__config>
-_LIBCPP_HIDE_FROM_ABI inline int f() { return 3; }
+_LIBCPP_HIDE_FROM_ABI TEST_NOINLINE inline int f() { return 3; }
 int tu3() { return f(); }
 #endif // TU3
 
 // No hardening
 #ifdef TU4
 #  include <__config>
-_LIBCPP_HIDE_FROM_ABI inline int f() { return 4; }
+_LIBCPP_HIDE_FROM_ABI TEST_NOINLINE inline int f() { return 4; }
 int tu4() { return f(); }
 #endif // TU4