Re: [PATCH v3 2/4] util: Introduce read_file() and read_file_long() function

On Wed, Oct 15, 2025 at 12:46 PM David Gibson wrote:

On Wed, Oct 15, 2025 at 11:50:53AM +0800, Yumei Huang wrote:

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On Wed, Oct 15, 2025 at 7:28 AM David Gibson wrote:

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On Tue, Oct 14, 2025 at 03:38:34PM +0800, Yumei Huang wrote:

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Signed-off-by: Yumei Huang [snip] + * @path: Path to the sysctl file + * @fallback: Default value if file can't be read + * + * Return: Parameter value, fallback on failure +*/ +long read_file_long(const char *path, long fallback) +{ + char buf[32];

Rather than just using a semi-arbitrary 32 here, I'd suggest defining a new constant similar to UINT16_STRLEN. Except that's trickier for a type that doesn't have a known fixed width. Pity the C library doesn't have constants for these AFAICT.

I will just define a UINTMAX_STRLEN with (sizeof("2147483647")).

That's not quite right. - It should be INTMAX_STRLEN (signed), UINTMAX would be for the unsigned version - That assumes intmax_t is 32-bit which is probably not the case (it will be 64-bit, maybe even 128-bit on modern systems) - For signed cases, it's the minimum (negative) value that gives the longest possible string (for 32-bit, "-2147483648")

Maybe we could take it as 64 bits for now? I'm not sure under which circumstance we would read such a large number. If you agree, the define could be: #define INTMAX_STRLEN (sizeof("-9223372036854775808")) Or maybe define it to 20 directly : #define INTMAX_STRLEN 20 what do you think?

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson

-- Thanks, Yumei Huang