fix isdigit taking unsigned as input
fixes the following error warnings when cross-compiling using:
./configure --enable-static --prefix=/usr/local/arm-none-eabi --host=arm-none-eabi --enable-embedded --disable-doxygen --disable-shared --disable-pseudotalloc --enable-external-tests CFLAGS="-Os -ffunction-sections -fdata-sections -nostartfiles -nodefaultlibs -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations -Wno-error=cpp -mthumb -Os -mlong-calls -g3 -mcpu=cortex-m4 -mfloat-abi=softfp -mfpu=fpv4-sp-d16 -Wno-error=format"
utils.c:1002:18: error: array subscript has type 'char' [-Werror=char-subscripts]
1002 | if (!isdigit(in[i]))
gsm23003.c:414:34: error: array subscript has type 'char' [-Werror=char-subscripts]
414 | if (!mnc_str || !isdigit(mnc_str[0]) || strlen(mnc_str) > 3)
Change-Id: Ia13fd5ee79fc6dc3291c0b99958ab3c01afee17d
diff --git a/src/utils.c b/src/utils.c
index 7b7178c..7364bfb 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -999,7 +999,7 @@
/* All input must be numbers */
for (i = 0; i < in_len; i++) {
- if (!isdigit(in[i]))
+ if (!isdigit((unsigned char)in[i]))
return -EINVAL;
}