# [PATCH] help: Fix size passed to qsort 3 messages from 2014-09-17 to 2014-09-18. Participants: Stefan Beller, Junio C Hamano. Thread: https://gitlist.dev/t/37583 ## Stefan Beller, 2014-09-17 12:14 Subject: [PATCH] help: Fix size passed to qsort Message-ID: <1410956079-23513-1-git-send-email-stefanbeller@gmail.com> URL: https://gitlist.dev/e/1410956079-23513-1-git-send-email-stefanbeller%40gmail.com ``` We actually want to have the size of one 'name' and not the size of the names array. Signed-off-by: Stefan Beller --- help.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/help.c b/help.c index 7af65e2..2072a87 100644 --- a/help.c +++ b/help.c @@ -305,7 +305,7 @@ const char *help_unknown_cmd(const char *cmd) add_cmd_list(&main_cmds, &aliases); add_cmd_list(&main_cmds, &other_cmds); qsort(main_cmds.names, main_cmds.cnt, - sizeof(main_cmds.names), cmdname_compare); + sizeof(*main_cmds.names), cmdname_compare); uniq(&main_cmds); /* This abuses cmdname->len for levenshtein distance */ -- 2.1.0.238.gce1d3a9 ``` ## Junio C Hamano, 2014-09-18 17:17 Subject: Re: [PATCH] help: Fix size passed to qsort Message-ID: URL: https://gitlist.dev/e/xmqq8ulgq25h.fsf%40gitster.dls.corp.google.com In-Reply-To: <1410956079-23513-1-git-send-email-stefanbeller@gmail.com> ``` Stefan Beller writes: > We actually want to have the size of one 'name' and not the size > of the names array. I suspect that the latter is "size of a pointer that points at a cmdname structure", but the original code in help_unknown_cmd() is wrong. The ones in load_command_list() do this correctly and another qsort() invocation in this function does so as well. I wonder why they didn't correctly cut&paste ;-) 746c221a (git wrapper: also use aliases to correct mistyped commands, 2008-09-10) seemed to have introduced the culprit. The call to uniq() would fail to uniquify because main_cmds would have the standard command all in front and then aliases and commands in the user's PATH later, but I do not quite see if there is any end-user observable breakages that can arise from this. What is the practical implication of this breakage? No, I am not saying we do not have to fix it; I am just being curious why this patch does not show the existing breakage with a new test. Thanks. > > Signed-off-by: Stefan Beller > --- > help.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/help.c b/help.c > index 7af65e2..2072a87 100644 > --- a/help.c > +++ b/help.c > @@ -305,7 +305,7 @@ const char *help_unknown_cmd(const char *cmd) > add_cmd_list(&main_cmds, &aliases); > add_cmd_list(&main_cmds, &other_cmds); > qsort(main_cmds.names, main_cmds.cnt, > - sizeof(main_cmds.names), cmdname_compare); > + sizeof(*main_cmds.names), cmdname_compare); > uniq(&main_cmds); > > /* This abuses cmdname->len for levenshtein distance */ ``` ## Junio C Hamano, 2014-09-18 17:34 Subject: Re: [PATCH] help: Fix size passed to qsort Message-ID: URL: https://gitlist.dev/e/xmqqzjdwomrr.fsf%40gitster.dls.corp.google.com In-Reply-To: ``` Junio C Hamano writes: > Stefan Beller writes: > >> We actually want to have the size of one 'name' and not the size >> of the names array. > ... > I suspect that the latter is "size of a pointer that points at a > cmdname structure", but the original code in help_unknown_cmd() is > wrong. The ones in load_command_list() do this correctly and > another qsort() invocation in this function does so as well. I > wonder why they didn't correctly cut&paste ;-) > > 746c221a (git wrapper: also use aliases to correct mistyped > commands, 2008-09-10) seemed to have introduced the culprit. > > The call to uniq() would fail to uniquify because main_cmds would > have the standard command all in front and then aliases and commands > in the user's PATH later, but I do not quite see if there is any > end-user observable breakages that can arise from this. What is the > practical implication of this breakage? Heh, I should have spent a bit more time before starting to type. The answer probably is "nothing", as struct cmdnames { ... struct cmdname { ... } **names; } main_cmds; is what we are dealing here, so main_cmds.names is a pointer that points at a slab of memory to hold many pointers, each of which points at "struct cmdname". And sizeof(struct cmdname **) is incorrectly passed where we should pass sizeof(struct cmdname *), which you fixed, but in practice they would be the same size anyway ;-) >> qsort(main_cmds.names, main_cmds.cnt, >> - sizeof(main_cmds.names), cmdname_compare); >> + sizeof(*main_cmds.names), cmdname_compare); >> uniq(&main_cmds); >> >> /* This abuses cmdname->len for levenshtein distance */ ```