linux-toradex.git/scripts/kconfig/tests/err_num_bounds/Kconfig, branch master Linux kernel for Apalis and Colibri modules kconfig: check for out-of-bounds numeric constants 2026-09-17T23:31:00+00:00 Julian Braha julianbraha@gmail.com 2026-09-15T21:15:05+00:00 a5e84d6f6df1fdb64c06fdb64894199aaf5ec899 The Kconfig interpreter internally represents constants as strings, then attempts to parse them as 64-bit signed integers for 'int' options, and 64-bit unsigned integers for 'hex' options. However, there is currently no check that the conversion succeeds, leading to failures when the values are actually used. For example: config LARGE_INT int default 10000000000000000000 config BUGGED_INT_COMPARISON bool default y if LARGE_INT < 2 Obviously 10000000000000000000 is larger than 2, but the Kconfig interpreter will fallback to comparing the two values with strcmp() after the numeric conversion fails, causing the first character, '1', to be compared with '2', and giving the wrong result. Since none of these out-of-bounds values are used as constants anywhere in the tree, we can already make these error out. Assisted-by: LLM Signed-off-by: Julian Braha <julianbraha@gmail.com> Reviewed-by: Nicolas Schier <n.schier@fritz.com> Link: https://patch.msgid.link/20260915211508.291790-3-julianbraha@gmail.com Signed-off-by: Nathan Chancellor <nathan@kernel.org> 
The Kconfig interpreter internally represents constants as strings, then
attempts to parse them as 64-bit signed integers for 'int' options, and
64-bit unsigned integers for 'hex' options.

However, there is currently no check that the conversion succeeds, leading
to failures when the values are actually used. For example:

  config LARGE_INT
    int
    default 10000000000000000000

  config BUGGED_INT_COMPARISON
    bool
    default y if LARGE_INT < 2

Obviously 10000000000000000000 is larger than 2, but the Kconfig
interpreter will fallback to comparing the two values with strcmp() after
the numeric conversion fails, causing the first character, '1', to be
compared with '2', and giving the wrong result.

Since none of these out-of-bounds values are used as constants anywhere in
the tree, we can already make these error out.

Assisted-by: LLM
Signed-off-by: Julian Braha <julianbraha@gmail.com>
Reviewed-by: Nicolas Schier <n.schier@fritz.com>
Link: https://patch.msgid.link/20260915211508.291790-3-julianbraha@gmail.com
Signed-off-by: Nathan Chancellor <nathan@kernel.org>