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	util: trim() fix for UB on pointer arithmetic - sic - simple irc client
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	---
	commit 058547e707e961e0cb7f8af4877f1b92f4c6d888
	parent 68c1c4e5110ed6a30cd3da0ae0c2ab0753e02cbb
	Author: Hiltjo Posthuma <[email protected]>
	Date: Thu, 6 May 2021 12:18:21 +0200

	util: trim() fix for UB on pointer arithmetic

	Follow-up fix on commit df4c0611366bf361fa263fbc57009cbe68456855

	"
	While it is true reversing the condition solves a single-byte read at
	one before s, there is a second instance of UB.

	Having a pointer to one before an object is in of itself UB in C, it's
	on the side of language lawyering, but it's UB.
	I add here a quote from a C standard draft:
	> When an expression that has integer type is added to or subtracted
	> from a pointer, the result has the type of the pointer operand.
	> If both the pointer operand and the result point to elements of the
	> same array object, or one past the last element of the array object,
	> the evaluation shall not produce an overflow; otherwise, the
	> behavior is undefined.
	Taken from: http://www.iso-9899.info/n1570.html#6.5.6p8
	"

	Thanks Guilherme Janczak <[email protected]>

	Diffstat:
	M util.c \| 7 +++----

	1 file changed, 3 insertions(+), 4 deletions(-)
	---
	diff --git a/util.c b/util.c
	@@ -60,8 +60,7 @@ static void
	trim(char *s) {
	char *e;

	- e = s + strlen(s) - 1;
	- while(e > s && isspace((unsigned char)*e))
	- e--;
	- *(e + 1) = '\0';
	+ for (e = s + strlen(s); e > s && isspace((unsigned char)*(e - 1)); e--)
	+ ;
	+ *e = '\0';
	}