Bug 406349

I believe that comes from -Wl,-z,interpose,-z,initfirst being included in PRELOAD_LDFLAGS_COMMON_LINUX in Makefile.all.am.

Now obviously we can avoid doing that for Android - obviously that might mean we are less successfully at interposing the functions we want to replace though.

Actually thinking about it we don't really rely on interposition these days, so do we really need those at all?

I think those flags were originally introduced in 918c3a7b7e01abedf840c6fa8786df41192bf737 by Jeremy way back in 2003!

These Text "linker: Warning: "/system_Q_EA3/lib64/valgrind/vgpreload_core-arm64-linux.so" has unsupported flags DT_FLAGS_1=0x421 (ignoring unsupported flags)" has been existed for several version from valgrind 3.12 and android 7 . and these version are all worked (valgrind can detect the memory leak). But only android Q  is failed.

Just to clarify: this warning always prints the full set of flags found in the DT_FLAGS_1 entry, including the supported ones, from its introduction at <https://cs.android.com/android/_/android/platform/bionic/+/6cdeb5234d7f4523fe9d83974f265d80f10512a6:linker/linker.cpp;drc=6cdeb5234d7f4523fe9d83974f265d80f10512a6;l=2067> to its current version at <https://cs.android.com/android/_/android/platform/bionic/+/7ea4c99263fb09c4590135e78bc26fa4e5786083:linker/linker.cpp;drc=7ea4c99263fb09c4590135e78bc26fa4e5786083;l=3186>.

The actual set of supported flags seems to range from `DF_1_NOW | DF_1_GLOBAL` to `DF_1_NOW | DF_1_GLOBAL | DF_1_NODELETE | DF_1_PIE | DF_1_ORIGIN`.

In any case, since `DF_1_INTERPOSE` and `DF_1_INITFIRST` never "worked" on Android, the warning is presumably unrelated to any regressions you're encountering with leak tracking.

Actually, there's an FAQ entry titled "Memcheck doesn't report any errors and I know my program has errors." at <https://valgrind.org/docs/manual/faq.html#faq.hiddenbug>; it seems likely that your issue was caused by statically linking libc or libc++ into your test program?

So this patch (totally untested because I don't have access to android) might get rid of the warnings:

diff --git a/Makefile.all.am b/Makefile.all.am
index d4f6b3fb7985..17427b48e97c 100644
--- a/Makefile.all.am
+++ b/Makefile.all.am
@@ -327,7 +327,15 @@ endif
 
 # Baseline link flags for making vgpreload shared objects.
 #
+if VGCONF_PLATVARIANT_IS_ANDROID
+# The Android toolchain includes all kinds of stdlib helpers present in
+# bionic which is bad because we are not linking with it and the Android
+# linker will panic. Also the Android runtime linker doesn't recognize
+# DF_1_INTERPOSE and DF_1_INITFIRST.
+PRELOAD_LDFLAGS_COMMON_LINUX  = -nodefaultlibs -shared -nostdlib
+else
 PRELOAD_LDFLAGS_COMMON_LINUX  = -nodefaultlibs -shared -Wl,-z,interpose,-z,initfirst
+endif
 PRELOAD_LDFLAGS_COMMON_FREEBSD  = -nodefaultlibs -shared -Wl,-z,interpose,-z,initfirst
 PRELOAD_LDFLAGS_COMMON_DARWIN = -dynamic -dynamiclib -all_load
 PRELOAD_LDFLAGS_COMMON_SOLARIS = -nodefaultlibs -shared -Wl,-z,interpose,-z,initfirst
@@ -335,13 +343,6 @@ if SOLARIS_XPG_SYMBOLS_PRESENT
 PRELOAD_LDFLAGS_COMMON_SOLARIS += -Wl,-M,$(top_srcdir)/solaris/vgpreload-solaris.mapfile
 endif
 
-if VGCONF_PLATVARIANT_IS_ANDROID
-# The Android toolchain includes all kinds of stdlib helpers present in
-# bionic which is bad because we are not linking with it and the Android
-# linker will panic.
-PRELOAD_LDFLAGS_COMMON_LINUX += -nostdlib
-endif
-
 PRELOAD_LDFLAGS_X86_LINUX      = $(PRELOAD_LDFLAGS_COMMON_LINUX) @FLAG_M32@
 PRELOAD_LDFLAGS_AMD64_LINUX    = $(PRELOAD_LDFLAGS_COMMON_LINUX) @FLAG_M64@
 PRELOAD_LDFLAGS_PPC32_LINUX    = $(PRELOAD_LDFLAGS_COMMON_LINUX) @FLAG_M32@

If someone could try that?

Still leaves the question why the original reporter doesn't seem to get any leakchecking.