Re: [PATCH v6 09/19] string: Make strstarts() a legacy alias for strprefix()

[Alejandro Colomar <alx@kernel.org>]

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> Date: 2026-11-14 15:33:19+0000
> From: sashiko-bot@kernel.org
>
> Thank you for your contribution! Sashiko AI review found 1 potential
> issue to consider:
> - [High] string: strstarts() macro expansion shadowed by local strprefix
>   variable
> --
> 
> commit e4b277f22320c7ff4dbc9e8cc88221ad43eb8ba6
> Author: Alejandro Colomar <alx@kernel.org>
> 
> string: Make strstarts() a legacy alias for strprefix()
> 
> This commit replaces the inline strstarts() function with a macro alias for
> strprefix().
> 
> > diff --git a/include/linux/string.h b/include/linux/string.h
> > index 013c6169def05..0a466360dbb39 100644
> > --- a/include/linux/string.h
> > +++ b/include/linux/string.h
> > @@ -609,6 +609,7 @@ static inline const char *strprefix(const char *s, const char *prefix)
> >  	return strncmp(s, prefix, len) == 0 ? s + len : NULL;
> >  }
> >  #define strprefix(s, pfx)  const_cast(CQChar_of(s) *, strprefix(s, pfx))
> > +#define strstarts(s, pfx)  strprefix(s, pfx)  // legacy alias
> 
> [Severity: High]
> Does expanding strstarts() to strprefix() break the build when a caller has
> a local variable named strprefix?
> 
> drivers/platform/x86/hp/hp-bioscfg/spmobj-attributes.c:hp_populate_security_buffer() {
> 	u16 *auth = authbuf;
> 	char *strprefix = NULL;
> 	int ret = 0;
> 
> 	if (strstarts(authentication, BEAM_PREFIX)) {
>     ...
> }
> 
> Because the strprefix() macro expands to a call to the inline function
> strprefix() in the caller's scope, the local pointer variable strprefix
> shadows the function identifier and breaks compilation when
> CONFIG_HP_BIOSCFG is enabled.  A later patch in this series, commit
> "platform/x86: hp-bioscfg: Rename local variable", renames that variable to
> prefix and should be ordered before this commit to keep the series
> bisectable.

This reivew is wrong.  A local variable cannot shadow a macro.  Also,
a function-like macro is only expanded if it's followed by an opening
parenthesis.  In the case of spmobj-attributes.c, the local variable
doesn't have a parenthesis, and thus doesn't trigger expansion.

> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/cover.1794667407.git.alx@kernel.org?part=9

-- 
<https://www.alejandro-colomar.es>

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