Re: Make psql ignore trailing semicolons in \sf, \ef, etc
Laurenz Albe writes: > On Mon, 2024-01-08 at 15:48 -0500, Tom Lane wrote: >> Is this enough of a bug to deserve back-patching? I'm not sure. > I like the patch, but I wouldn't back-patch it. I'd call the current > behavior a slight inconsistency rather than an outright bug, and I think > that we should be conservative with back-patching. Nobody spoke in favor of back-patching, so committed to HEAD only. regards, tom lane
Re: Make psql ignore trailing semicolons in \sf, \ef, etc
On Mon Jan 8, 2024 at 6:08 PM CST, Tom Lane wrote: "Tristan Partin" writes: > On Mon Jan 8, 2024 at 2:48 PM CST, Tom Lane wrote: >> +(isascii((unsigned char) mybuf.data[mybuf.len - 1]) && >> + isspace((unsigned char) mybuf.data[mybuf.len - 1] > Seems like if there was going to be any sort of casting, it would be to > an int, which is what the man page says for these two function, though > isascii(3) explicitly mentions "unsigned char." Casting to unsigned char is our standard pattern for using these functions. If "char" is signed (which is the only case in which this changes anything) then casting to int would imply sign-extension of the char's high-order bit, which is exactly what must not happen in order to produce a legal value to be passed to these functions. POSIX says: The c argument is an int, the value of which the application shall ensure is a character representable as an unsigned char or equal to the value of the macro EOF. If the argument has any other value, the behavior is undefined. If we cast to unsigned char, then the subsequent implicit cast to int will do zero-extension which is what we need. Thanks for the explanation. > Small English nit-pick: I would drop the hyphen between semi and colons. Me too, except that it's spelled like that in nearby comments. Shall I change them all? I'll leave it up to you. Patch looks good as-is. -- Tristan Partin Neon (https://neon.tech)
Re: Make psql ignore trailing semicolons in \sf, \ef, etc
On Mon, 2024-01-08 at 15:48 -0500, Tom Lane wrote: > Is this enough of a bug to deserve back-patching? I'm not sure. I like the patch, but I wouldn't back-patch it. I'd call the current behavior a slight inconsistency rather than an outright bug, and I think that we should be conservative with back-patching. Yours, Laurenz Albe
Re: Make psql ignore trailing semicolons in \sf, \ef, etc
"Tristan Partin" writes: > On Mon Jan 8, 2024 at 2:48 PM CST, Tom Lane wrote: >> +(isascii((unsigned char) >> mybuf.data[mybuf.len - 1]) && >> + isspace((unsigned char) >> mybuf.data[mybuf.len - 1] > Seems like if there was going to be any sort of casting, it would be to > an int, which is what the man page says for these two function, though > isascii(3) explicitly mentions "unsigned char." Casting to unsigned char is our standard pattern for using these functions. If "char" is signed (which is the only case in which this changes anything) then casting to int would imply sign-extension of the char's high-order bit, which is exactly what must not happen in order to produce a legal value to be passed to these functions. POSIX says: The c argument is an int, the value of which the application shall ensure is a character representable as an unsigned char or equal to the value of the macro EOF. If the argument has any other value, the behavior is undefined. If we cast to unsigned char, then the subsequent implicit cast to int will do zero-extension which is what we need. > Small English nit-pick: I would drop the hyphen between semi and colons. Me too, except that it's spelled like that in nearby comments. Shall I change them all? regards, tom lane
Re: Make psql ignore trailing semicolons in \sf, \ef, etc
On Mon Jan 8, 2024 at 2:48 PM CST, Tom Lane wrote:
We had a complaint (see [1], but it's not the first IIRC) about how
psql doesn't behave very nicely if one ends \sf or allied commands
with a semicolon:
regression=# \sf sin(float8);
ERROR: expected a right parenthesis
This is a bit of a usability gotcha, since many other backslash
commands are forgiving about trailing semicolons. I looked at
the code and found that it's actually trying to ignore semicolons,
by passing semicolon = true to psql_scan_slash_option. But that
fails to work because it's also passing type = OT_WHOLE_LINE,
and the whole-line code path ignores the semicolon flag. Probably
that's just because nobody needed to use that combination back in
the day. There's another user of OT_WHOLE_LINE, exec_command_help,
which also wants this behavior and has written its own stripping
code to get it. That seems pretty silly, so here's a quick finger
exercise to move that logic into psql_scan_slash_option.
Is this enough of a bug to deserve back-patching? I'm not sure.
regards, tom lane
[1]
https://www.postgresql.org/message-id/CAEs%3D6D%3DnwX2wm0hjkaw6C_LnqR%2BNFtnnzbSzeZq-xcfi_ooKSw%40mail.gmail.com
+/*
+ * In whole-line mode, we interpret semicolon = true
as stripping
+ * trailing whitespace as well as semi-colons; this
gives the
+ * nearest equivalent to what semicolon = true does
in normal
+ * mode. Note there's no concept of quoting in this
mode.
+ */
+if (semicolon)
+{
+while (mybuf.len > 0 &&
+ (mybuf.data[mybuf.len - 1] == ';'
||
+(isascii((unsigned char)
mybuf.data[mybuf.len - 1]) &&
+ isspace((unsigned char)
mybuf.data[mybuf.len - 1]
+{
+mybuf.data[--mybuf.len] = '\0';
+}
+}
Seems like if there was going to be any sort of casting, it would be to
an int, which is what the man page says for these two function, though
isascii(3) explicitly mentions "unsigned char."
Small English nit-pick: I would drop the hyphen between semi and colons.
As for backpatching, seems useful in the sense that people can write the
same script for all supported version of Postgres using the relaxed
syntax.
--
Tristan Partin
Neon (https://neon.tech)
