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Subject[PATCH v5] kconfig: avoid an infinite loop in oldconfig/syncconfig
Date
Exit on error when asking for value and reading stdin returns an error
(mainly if it has reached EOF or is closed).

This infinite loop happens in particular for hex/int configs without an
explicit default value.

Previously, this case would loop:
* oldconfig prompts for the value but stdin has reached EOF
* It gets the global default value : an empty string
* This is not a valid hex/int value so it prompts again, hence the
infinite loop.

This case happens with a configuration like this (a hex config without a
valid default value):
config TEST_KCONFIG
hex "Test KConfig"
# default 0x0

And using:
make oldconfig < /dev/null

This was discovered when working on Yocto bug[0] on a downstream
kconfig user (U-boot)

[0]: https://bugzilla.yoctoproject.org/show_bug.cgi?id=14136

CC: Brandon Maier <brandon.maier@collins.com>
Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
---
v4->v5:
* Switched to Masahiro Yamada's suggested code.
v3->v4:
* Added Brandon Maier's "Tested-by". Thanks!
v2->v3:
* Simplify the patch by fusing comments of :
* Masahiro Yamada : Exit as soon as reading stdin hits an error
* Randy Dunlap : Display the name of the currently read symbol
v1->v2:
* Improve coding style
* Put more info in the commit message
---
scripts/kconfig/conf.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/scripts/kconfig/conf.c b/scripts/kconfig/conf.c
index 33d19e419908..62de1fbaff97 100644
--- a/scripts/kconfig/conf.c
+++ b/scripts/kconfig/conf.c
@@ -76,8 +76,10 @@ static void strip(char *str)
/* Helper function to facilitate fgets() by Jean Sacren. */
static void xfgets(char *str, int size, FILE *in)
{
- if (!fgets(str, size, in))
+ if (!fgets(str, size, in)) {
fprintf(stderr, "\nError in reading or end of file.\n");
+ exit(1);
+ }

if (!tty_stdio)
printf("%s", str);
--
2.30.2
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