From: Chris Down <chris@chrisdown.name>
To: zsh-workers@zsh.org
Subject: [PATCH ALTERNATE] builtins: kill: Do not set signal on current pgroup when pid is empty
Date: Sat, 15 Feb 2020 09:52:48 -0400 [thread overview]
Message-ID: <20200215135248.GA662294@chrisdown.name> (raw)
In-Reply-To: <20200214151556.GA624243@chrisdown.name>
This was first noticed in the `kill` builtin:
% zsh; echo "$?"
% trap 'exit 5' TERM
% kill ''
5
This behaviour seems more likely to be the result of bugs in programs
(eg. `kill -9 "$unsetvar") rather than be desirable behaviour to me. It
seems unintentional judging by the code and documentation, since it
comes about as a result of the fact that:
- `isanum` returns true for empty strings (since an empty string
technically only consists of digits and minuses...);
- `atoi`, when passed a pointer to an invalid number, returns 0;
- kill(0, signal) sends the signal in question to all processes in the
current process group.
There are two ways to solve this issue:
1. Add special handling to `kill` to avoid this case. See this patch[0]
for a version that does that.
2. Change how isanum behaves. Since the only two call sites that use it
both seem like they should handle the case where the input char array
is empty, that seems like a reasonable overall change to me, but
either works.
After this patch:
% trap 'exit 5' TERM
% kill ''
kill: illegal pid:
0: https://www.zsh.org/mla/workers/2020/msg00251.html
---
Src/jobs.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/Src/jobs.c b/Src/jobs.c
index e7438251e..0485f2c7c 100644
--- a/Src/jobs.c
+++ b/Src/jobs.c
@@ -1854,13 +1854,14 @@ scanjobs(void)
/* This simple function indicates whether or not s may represent *
* a number. It returns true iff s consists purely of digits and *
- * minuses. Note that minus may appear more than once, and the empty *
- * string will produce a `true' response. */
+ * minuses. Note that minus may appear more than once. */
/**/
static int
isanum(char *s)
{
+ if (*s == '\0')
+ return 0;
while (*s == '-' || idigit(*s))
s++;
return *s == '\0';
--
2.25.0
next prev parent reply other threads:[~2020-02-15 13:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 15:15 [PATCH] builtins: kill: Do not set signal on current shell " Chris Down
2020-02-14 16:02 ` Chris Down
2020-02-15 13:52 ` Chris Down [this message]
2020-02-15 14:10 ` [PATCH ALTERNATE] builtins: kill: Do not set signal on current pgroup " Daniel Shahaf
2020-02-15 15:15 ` Chris Down
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