[PATCH] selftests/bpf: add -std=gnu11 to BPF_CFLAGS and CFLAGS

[PATCH] selftests/bpf: add -std=gnu11 to BPF_CFLAGS and CFLAGS

[Ihor Solodrai]

Latest versions of GCC BPF use C23 standard by default. This causes
compilation errors in vmlinux.h due to bool types declarations.

Add -std=gnu11 to BPF_CFLAGS and CFLAGS. This aligns with the version
of the standard used when building the kernel currently [1].

For more details see the discussions at [2] and [3].

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile#n465
[2] https://lore.kernel.org/bpf/EYcXjcKDCJY7Yb0GGtAAb7nLKPEvrgWdvWpuNzXm2qi6rYMZDixKv5KwfVVMBq17V55xyC-A1wIjrqG3aw-Imqudo9q9X7D7nLU2gWgbN0w=@pm.me/
[3] https://lore.kernel.org/bpf/20250106202715.1232864-1-ihor.solodrai@pm.me/

CC: Jose E. Marchesi <jose.marchesi@oracle.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@pm.me>
---
 tools/testing/selftests/bpf/Makefile | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index d5be2f94deef..ea9cee5de0f8 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -41,7 +41,7 @@ srctree := $(patsubst %/,%,$(dir $(srctree)))
 srctree := $(patsubst %/,%,$(dir $(srctree)))
 endif
 
-CFLAGS += -g $(OPT_FLAGS) -rdynamic					\
+CFLAGS += -g $(OPT_FLAGS) -rdynamic -std=gnu11				\
 	  -Wall -Werror -fno-omit-frame-pointer				\
 	  $(GENFLAGS) $(SAN_CFLAGS) $(LIBELF_CFLAGS)			\
 	  -I$(CURDIR) -I$(INCLUDE_DIR) -I$(GENDIR) -I$(LIBDIR)		\
@@ -447,6 +447,7 @@ CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
 BPF_CFLAGS = -g -Wall -Werror -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN)	\
 	     -I$(INCLUDE_DIR) -I$(CURDIR) -I$(APIDIR)			\
 	     -I$(abspath $(OUTPUT)/../usr/include)			\
+	     -std=gnu11		 					\
 	     -fno-strict-aliasing 					\
 	     -Wno-compare-distinct-pointer-types
 # TODO: enable me -Wsign-compare
@@ -787,9 +788,12 @@ $(OUTPUT)/xdp_features: xdp_features.c $(OUTPUT)/network_helpers.o $(OUTPUT)/xdp
 	$(Q)$(CC) $(CFLAGS) $(filter %.a %.o %.c,$^) $(LDLIBS) -o $@
 
 # Make sure we are able to include and link libbpf against c++.
+CXXFLAGS += $(CFLAGS)
+CXXFLAGS := $(subst -D_GNU_SOURCE=,,$(CXXFLAGS))
+CXXFLAGS := $(subst -std=gnu11,-std=gnu++11,$(CXXFLAGS))
 $(OUTPUT)/test_cpp: test_cpp.cpp $(OUTPUT)/test_core_extern.skel.h $(BPFOBJ)
 	$(call msg,CXX,,$@)
-	$(Q)$(CXX) $(subst -D_GNU_SOURCE=,,$(CFLAGS)) $(filter %.a %.o %.cpp,$^) $(LDLIBS) -o $@
+	$(Q)$(CXX) $(CXXFLAGS) $(filter %.a %.o %.cpp,$^) $(LDLIBS) -o $@
 
 # Benchmark runner
 $(OUTPUT)/bench_%.o: benchs/bench_%.c bench.h $(BPFOBJ)
-- 
2.47.1

Re: [PATCH] selftests/bpf: add -std=gnu11 to BPF_CFLAGS and CFLAGS

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Tue, 07 Jan 2025 23:58:18 +0000 you wrote:
> Latest versions of GCC BPF use C23 standard by default. This causes
> compilation errors in vmlinux.h due to bool types declarations.
> 
> Add -std=gnu11 to BPF_CFLAGS and CFLAGS. This aligns with the version
> of the standard used when building the kernel currently [1].
> 
> For more details see the discussions at [2] and [3].
> 
> [...]

Here is the summary with links:
  - selftests/bpf: add -std=gnu11 to BPF_CFLAGS and CFLAGS
    https://git.kernel.org/bpf/bpf-next/c/bab18c7db44d

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH] selftests/bpf: add -std=gnu11 to BPF_CFLAGS and CFLAGS

[Andrii Nakryiko]

On Tue, Jan 7, 2025 at 3:58 PM Ihor Solodrai <ihor.solodrai@pm.me> wrote:
>
> Latest versions of GCC BPF use C23 standard by default. This causes
> compilation errors in vmlinux.h due to bool types declarations.

Do you have an example of an error? Why can't we fix that to work with C23?

>
> Add -std=gnu11 to BPF_CFLAGS and CFLAGS. This aligns with the version
> of the standard used when building the kernel currently [1].
>
> For more details see the discussions at [2] and [3].
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile#n465
> [2] https://lore.kernel.org/bpf/EYcXjcKDCJY7Yb0GGtAAb7nLKPEvrgWdvWpuNzXm2qi6rYMZDixKv5KwfVVMBq17V55xyC-A1wIjrqG3aw-Imqudo9q9X7D7nLU2gWgbN0w=@pm.me/
> [3] https://lore.kernel.org/bpf/20250106202715.1232864-1-ihor.solodrai@pm.me/
>
> CC: Jose E. Marchesi <jose.marchesi@oracle.com>
> Signed-off-by: Ihor Solodrai <ihor.solodrai@pm.me>
> ---
>  tools/testing/selftests/bpf/Makefile | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index d5be2f94deef..ea9cee5de0f8 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -41,7 +41,7 @@ srctree := $(patsubst %/,%,$(dir $(srctree)))
>  srctree := $(patsubst %/,%,$(dir $(srctree)))
>  endif
>
> -CFLAGS += -g $(OPT_FLAGS) -rdynamic                                    \
> +CFLAGS += -g $(OPT_FLAGS) -rdynamic -std=gnu11                         \
>           -Wall -Werror -fno-omit-frame-pointer                         \
>           $(GENFLAGS) $(SAN_CFLAGS) $(LIBELF_CFLAGS)                    \
>           -I$(CURDIR) -I$(INCLUDE_DIR) -I$(GENDIR) -I$(LIBDIR)          \
> @@ -447,6 +447,7 @@ CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
>  BPF_CFLAGS = -g -Wall -Werror -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN)    \
>              -I$(INCLUDE_DIR) -I$(CURDIR) -I$(APIDIR)                   \
>              -I$(abspath $(OUTPUT)/../usr/include)                      \
> +            -std=gnu11                                                 \
>              -fno-strict-aliasing                                       \
>              -Wno-compare-distinct-pointer-types
>  # TODO: enable me -Wsign-compare
> @@ -787,9 +788,12 @@ $(OUTPUT)/xdp_features: xdp_features.c $(OUTPUT)/network_helpers.o $(OUTPUT)/xdp
>         $(Q)$(CC) $(CFLAGS) $(filter %.a %.o %.c,$^) $(LDLIBS) -o $@
>
>  # Make sure we are able to include and link libbpf against c++.
> +CXXFLAGS += $(CFLAGS)
> +CXXFLAGS := $(subst -D_GNU_SOURCE=,,$(CXXFLAGS))
> +CXXFLAGS := $(subst -std=gnu11,-std=gnu++11,$(CXXFLAGS))
>  $(OUTPUT)/test_cpp: test_cpp.cpp $(OUTPUT)/test_core_extern.skel.h $(BPFOBJ)
>         $(call msg,CXX,,$@)
> -       $(Q)$(CXX) $(subst -D_GNU_SOURCE=,,$(CFLAGS)) $(filter %.a %.o %.cpp,$^) $(LDLIBS) -o $@
> +       $(Q)$(CXX) $(CXXFLAGS) $(filter %.a %.o %.cpp,$^) $(LDLIBS) -o $@
>
>  # Benchmark runner
>  $(OUTPUT)/bench_%.o: benchs/bench_%.c bench.h $(BPFOBJ)
> --
> 2.47.1
>
>
>

Re: [PATCH] selftests/bpf: add -std=gnu11 to BPF_CFLAGS and CFLAGS

[Ihor Solodrai]

On Friday, January 10th, 2025 at 3:34 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:

> 
> 
> On Tue, Jan 7, 2025 at 3:58 PM Ihor Solodrai ihor.solodrai@pm.me wrote:
> 
> > Latest versions of GCC BPF use C23 standard by default. This causes
> > compilation errors in vmlinux.h due to bool types declarations.
> 
> 
> Do you have an example of an error? Why can't we fix that to work with C23?

See a thread here: https://lore.kernel.org/bpf/ZryncitpWOFICUSCu4HLsMIZ7zOuiH5f4jrgjAh0uiOgKvZzQES09eerwIXNonKEq0U6hdI9pHSCPahUKihTeS8NKlVfkcuiRLotteNbQ9I=@pm.me/

The one I ran into is about:

    enum {
    	false = 0,
    	true = 1,
    };

Which is illegal in C23, because true and false are reserved words.

> 
> [...]

Re: [PATCH] selftests/bpf: add -std=gnu11 to BPF_CFLAGS and CFLAGS

[Andrii Nakryiko]

On Fri, Jan 10, 2025 at 3:44 PM Ihor Solodrai <ihor.solodrai@pm.me> wrote:
>
> On Friday, January 10th, 2025 at 3:34 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> >
> >
> > On Tue, Jan 7, 2025 at 3:58 PM Ihor Solodrai ihor.solodrai@pm.me wrote:
> >
> > > Latest versions of GCC BPF use C23 standard by default. This causes
> > > compilation errors in vmlinux.h due to bool types declarations.
> >
> >
> > Do you have an example of an error? Why can't we fix that to work with C23?
>
> See a thread here: https://lore.kernel.org/bpf/ZryncitpWOFICUSCu4HLsMIZ7zOuiH5f4jrgjAh0uiOgKvZzQES09eerwIXNonKEq0U6hdI9pHSCPahUKihTeS8NKlVfkcuiRLotteNbQ9I=@pm.me/
>

Yeah, thanks, still catching up, just got to that thread and saw the
discussion. What a mess, I'll pretend I don't know about this. :)

> The one I ran into is about:
>
>     enum {
>         false = 0,
>         true = 1,
>     };
>
> Which is illegal in C23, because true and false are reserved words.
>
> >
> > [...]