musl - strtod doesn't set errno to ERANGE for slightly out-of-range hex float

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Message-ID: <5a87ad28-d300-4c06-a60a-fa97a4d0d691@lenardszolnoki.com>
Date: Mon, 24 Mar 2025 10:55:36 +0000
From: Lénárd Szolnoki <cpp@...ardszolnoki.com>
To: musl@...ts.openwall.com
Subject: strtod doesn't set errno to ERANGE for slightly out-of-range hex
 float

Hi,

#include <stdlib.h>
#include <assert.h>
#include <errno.h>

int main() {
   const char* const input = "0x1.fffffffffffff8p+1023";
   double ret = strtod(input, NULL);
   assert(errno == ERANGE);
}

The input is slightly out of range, DBL_MAX is 1.fffffffffffffp+1023 (one fewer binary 1 
in the mantissa).

The assert fails with musl libc, passes with glibc.

musl version: 1.2.5 (as shipped in Debian sid)

Regards,
Lénárd Szolnoki

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