[Buildroot] [PATCH] support/bootlin-toolchains: don't depend on non-existent gcc version

[Arnout Vandecappelle]

On 07/10/2023 22:57, Yann E. MORIN wrote:
> Commit a0d2a5cfec0a (support/scripts/gen-bootlin-toolchains: generate
> BR2_ARCH_NEEDS_GCC_AT_LEAST_X guard) added a negative dependency to the
> gcc version required by the configured architecture.
> 
> However, when the toolchain is using the latest gcc version currently
> known to Buildroot, this generates a dependency on a non-existing gcc
> version. For example, a toolchain using gcc 13, the most recent version
> currently known to Buildroot, this would generate a dependency against
> BR2_ARCH_NEEDS_GCC_AT_LEAST_14, which does not exist yet.

  That means, however, that if we add GCC 14, we need to remember to add the 
condition to the Bootlin toolchains again... Of course, that can easily be 
solved by regenerating them, but we don't currently do that when adding a new 
GCC version.

  So really, I would feel more comfortable just adding the symbols for GCC 14 
support already.

  Regards,
  Arnout

> 
> This dependency is in practice a no-op, because the symbol is missing,
> so Kconfig evaluates it to false, and since it is negated, the
> dependency is fulfilled. Still, this is spurious and semantically
> incorrect.
> 
> We fix that by extracting the most recent gcc version that an
> architecture may require, and use that to decide whether the guard is
> needed for the toolchain.
> 
> Signed-off-by: Yann E. MORIN <yann.morin.1998 at free.fr>
> Cc: Vincent Fazio <vfazio at xes-inc.com>
> ---
>   support/scripts/gen-bootlin-toolchains | 19 ++++++++++++++++---
>   1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/support/scripts/gen-bootlin-toolchains b/support/scripts/gen-bootlin-toolchains
> index 4344221213..3b5f65515d 100755
> --- a/support/scripts/gen-bootlin-toolchains
> +++ b/support/scripts/gen-bootlin-toolchains
> @@ -305,7 +305,7 @@ class Toolchain:
>           return os.path.join(BASE_URL, self.arch, "fragments",
>                               self.fname_prefix + ".frag")
>   
> -    def gen_config_in_options(self, f):
> +    def gen_config_in_options(self, f, latest_gcc):
>           f.write("config %s\n" % self.option_name)
>           f.write("\tbool \"%s %s %s %s\"\n" %
>                   (self.arch, self.libc, self.variant, self.version))
> @@ -339,7 +339,8 @@ class Toolchain:
>                   assert m, "Cannot get gcc version for toolchain %s" % self.fname_prefix
>                   selects.append("BR2_TOOLCHAIN_GCC_AT_LEAST_%s" % m[1])
>                   # respect the GCC requirement for the selected CPU/arch tuning
> -                depends.append("!BR2_ARCH_NEEDS_GCC_AT_LEAST_%s" % str(int(m[1]) + 1))
> +                if int(m[1]) + 1 <= latest_gcc:
> +                    depends.append("!BR2_ARCH_NEEDS_GCC_AT_LEAST_%s" % str(int(m[1]) + 1))
>   
>               # kernel headers version
>               if frag.startswith("BR2_TOOLCHAIN_EXTERNAL_HEADERS_"):
> @@ -462,6 +463,17 @@ class Toolchain:
>               (self.arch, self.libc, self.variant, self.version, self.option_name)
>   
>   
> +def get_latest_gcc():
> +    match = "config BR2_ARCH_NEEDS_GCC_AT_LEAST_"
> +    with open("arch/Config.in", "r") as f:
> +        latest = sorted([
> +            int(line[len(match):].strip().split("_")[0])
> +            for line in f.readlines()
> +            if line.startswith(match)
> +        ])[-1]
> +    return latest
> +
> +
>   def get_toolchains():
>       toolchains = list()
>       for arch, details in arches.items():
> @@ -494,6 +506,7 @@ def get_toolchains():
>   
>   
>   def gen_config_in_options(toolchains, fpath):
> +    latest_gcc = get_latest_gcc()
>       with open(fpath, "w") as f:
>           f.write(AUTOGENERATED_COMMENT)
>   
> @@ -520,7 +533,7 @@ def gen_config_in_options(toolchains, fpath):
>           f.write("\tprompt \"Bootlin toolchain variant\"\n")
>   
>           for toolchain in toolchains:
> -            toolchain.gen_config_in_options(f)
> +            toolchain.gen_config_in_options(f, latest_gcc)
>   
>           f.write("endchoice\n")
>           f.write("endif\n")