When building with clang via:

    make LLVM=1 -C tools/testing/selftests

two distinct failures occur:

1) gcc requires -static-libasan in order to ensure that Address
Sanitizer's library is the first one loaded. However, this leads to
build failures on clang, when building via:

       make LLVM=1 -C tools/testing/selftests

However, clang already does the right thing by default: it statically
links the Address Sanitizer if -fsanitize is specified. Therefore, fix
this by simply omitting -static-libasan for clang builds. And leave
behind a comment, because the whole reason for static linking might not
be obvious.

2) clang won't accept invocations of this form, but gcc will:

    $(CC) file1.c header2.h

Fix this by using selftests/lib.mk facilities for tracking local header
file dependencies: add them to LOCAL_HDRS, leaving only the .c files to
be passed to the compiler.

Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 tools/testing/selftests/openat2/Makefile | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/openat2/Makefile b/tools/testing/selftests/openat2/Makefile
index 254d676a2689..185dc76ebb5f 100644
--- a/tools/testing/selftests/openat2/Makefile
+++ b/tools/testing/selftests/openat2/Makefile
@@ -1,8 +1,18 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
-CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined -static-libasan
+CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined
 TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test
 
+# gcc requires -static-libasan in order to ensure that Address Sanitizer's
+# library is the first one loaded. However, clang already statically links the
+# Address Sanitizer if -fsanitize is specified. Therefore, simply omit
+# -static-libasan for clang builds.
+ifeq ($(LLVM),)
+    CFLAGS += -static-libasan
+endif
+
+LOCAL_HDRS += helpers.h
+
 include ../lib.mk
 
-$(TEST_GEN_PROGS): helpers.c helpers.h
+$(TEST_GEN_PROGS): helpers.c
-- 
2.45.1

On Fri, May 31, 2024 at 06:45:33PM -0700, John Hubbard wrote:
> When building with clang via:
> 
>     make LLVM=1 -C tools/testing/selftests
> 
> two distinct failures occur:
> 
> 1) gcc requires -static-libasan in order to ensure that Address
> Sanitizer's library is the first one loaded. However, this leads to
> build failures on clang, when building via:
> 
>        make LLVM=1 -C tools/testing/selftests
> 
> However, clang already does the right thing by default: it statically
> links the Address Sanitizer if -fsanitize is specified. Therefore, fix
> this by simply omitting -static-libasan for clang builds. And leave
> behind a comment, because the whole reason for static linking might not
> be obvious.
> 
> 2) clang won't accept invocations of this form, but gcc will:
> 
>     $(CC) file1.c header2.h
> 
> Fix this by using selftests/lib.mk facilities for tracking local header
> file dependencies: add them to LOCAL_HDRS, leaving only the .c files to
> be passed to the compiler.
> 
> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>

Assuming that $(LLVM) is the correct conditional to test for:

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  tools/testing/selftests/openat2/Makefile | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/openat2/Makefile b/tools/testing/selftests/openat2/Makefile
> index 254d676a2689..185dc76ebb5f 100644
> --- a/tools/testing/selftests/openat2/Makefile
> +++ b/tools/testing/selftests/openat2/Makefile
> @@ -1,8 +1,18 @@
>  # SPDX-License-Identifier: GPL-2.0-or-later
>  
> -CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined -static-libasan
> +CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined
>  TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test
>  
> +# gcc requires -static-libasan in order to ensure that Address Sanitizer's
> +# library is the first one loaded. However, clang already statically links the
> +# Address Sanitizer if -fsanitize is specified. Therefore, simply omit
> +# -static-libasan for clang builds.
> +ifeq ($(LLVM),)
> +    CFLAGS += -static-libasan
> +endif
> +
> +LOCAL_HDRS += helpers.h
> +
>  include ../lib.mk
>  
> -$(TEST_GEN_PROGS): helpers.c helpers.h
> +$(TEST_GEN_PROGS): helpers.c
> -- 
> 2.45.1
> 
>

On Fri, May 31, 2024 at 06:45:33PM -0700, John Hubbard wrote:
> When building with clang via:
> 
>     make LLVM=1 -C tools/testing/selftests
> 
> two distinct failures occur:
> 
> 1) gcc requires -static-libasan in order to ensure that Address
> Sanitizer's library is the first one loaded. However, this leads to
> build failures on clang, when building via:
> 
>        make LLVM=1 -C tools/testing/selftests
> 
> However, clang already does the right thing by default: it statically
> links the Address Sanitizer if -fsanitize is specified. Therefore, fix
> this by simply omitting -static-libasan for clang builds. And leave
> behind a comment, because the whole reason for static linking might not
> be obvious.
> 
> 2) clang won't accept invocations of this form, but gcc will:
> 
>     $(CC) file1.c header2.h
> 
> Fix this by using selftests/lib.mk facilities for tracking local header
> file dependencies: add them to LOCAL_HDRS, leaving only the .c files to
> be passed to the compiler.
> 
> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>

Assuming that $(LLVM) is the correct conditional to test for:

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  tools/testing/selftests/openat2/Makefile | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/openat2/Makefile b/tools/testing/selftests/openat2/Makefile
> index 254d676a2689..185dc76ebb5f 100644
> --- a/tools/testing/selftests/openat2/Makefile
> +++ b/tools/testing/selftests/openat2/Makefile
> @@ -1,8 +1,18 @@
>  # SPDX-License-Identifier: GPL-2.0-or-later
>  
> -CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined -static-libasan
> +CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined
>  TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test
>  
> +# gcc requires -static-libasan in order to ensure that Address Sanitizer's
> +# library is the first one loaded. However, clang already statically links the
> +# Address Sanitizer if -fsanitize is specified. Therefore, simply omit
> +# -static-libasan for clang builds.
> +ifeq ($(LLVM),)
> +    CFLAGS += -static-libasan
> +endif
> +
> +LOCAL_HDRS += helpers.h
> +
>  include ../lib.mk
>  
> -$(TEST_GEN_PROGS): helpers.c helpers.h
> +$(TEST_GEN_PROGS): helpers.c
> -- 
> 2.45.1
> 
>