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Message-ID: <20260907235219.GF23438@brightrain.aerifal.cx>
Date: Mon, 7 Sep 2026 19:52:20 -0400
From: Rich Felker <dalias@...c.org>
To: Lukas Tribus <lukas@...i.eu>
Cc: musl@...ts.openwall.com, rafamiga <rafamiga@...il.com>
Subject: Re: Type confusion in include/sched.h (was: Discrepancy in include/sched.h – breaks haproxy's CPU topology discovery)
On Sun, Mar 22, 2026 at 04:41:41PM +0100, Lukas Tribus wrote:
> Dear list,
>
>
> On Fri, 5 Sept 2025 at 21:23, rafamiga <rafamiga@...il.com> wrote:
> >
> > While working on a fix for haproxy load balancer running in a container built with musl a discrepancy was found in include/sched.h. Long story short, on a 48 CPU system haproxy was reporting just 32 CPUs. I'm forwarding findings to this list to let you know that a change might be considered.
> >
> > Original bug report: https://github.com/haproxy/haproxy/issues/3103
> >
> > Citing the author (wtarreau):
> >
> > Oh I think I found it! The issue is here in sched.h:
> >
> > #define __CPU_op_S(i, size, set, op) ( (i)/8U >= (size) ? 0 : \
> > (((unsigned long *)(set))[(i)/8/sizeof(long)] op (1UL<<((i)%(8*sizeof(long))))) )
> >
> > but CPU_ISSET() is defined as:
> >
> > #define CPU_ISSET(i, set) CPU_ISSET_S(i,sizeof(cpu_set_t),set)
> >
> > See ? It returns an unsigned long which is returned as-is by the macro. However the man says that CPU_ISSET() must return an int. So in our case it's returned as-is and truncated to the lowest 32 bits.
> >
> > The fix for the lib would be simple:
> >
> > -#define CPU_ISSET(i, set) CPU_ISSET_S(i,sizeof(cpu_set_t),set)
> > +#define CPU_ISSET(i, set) (CPU_ISSET_S(i,sizeof(cpu_set_t),set) != 0)
> >
> > It should be reported to the project.
>
>
> Any feedback on the above report regarding a unsigned long vs int type
> mismatch and the change suggested by Willy Tarreau?
Sorry this got overlooked. I'm fixing it now.
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