Zsh Mailing List Archive
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printf bug(s?)


I'll get right to the point.


When I run the command printf '%', zsh 4.2.5 gives me a segfault. It
should complain that % by itself is invalid instead. I digged around a
bit and it seems to be caused by zsh mistakenly treating '\0' as a valid
flag character. This part is easy enough to work around:

--- zsh-4.2.5.orig/Src/builtin.c
+++ zsh-4.2.5/Src/builtin.c
@@ -3651,7 +3651,7 @@

            /* copy only one of each flag as spec has finite size */
            memset(flags, 0, sizeof(flags));
-           while ((flag = strchr(flagch, *c))) {
+           while (*c!='\0' && (flag = strchr(flagch, *c))) {
                if (!flags[flag - flagch]) {
                    flags[flag - flagch] = 1;
                    *d++ = *c;

If *c=='\0', strchr doesn't return NULL, but instead, it returns a
pointer to the terminating '\0', so this case should get special treatment.

With this patch, zsh now prints
printf: %: invalid directive
which I consider more sane :-)

But perhaps there's a nicer way to scan for flag characters.


That segfault I noticed when I tried to run printf '\045'. I expected
this to print a single character '%', the same as printf '%%' would. zsh
instead treats it exactly as an ordinary % character. Is this a bug, or
am I wrong to expect it to print '%'? I checked the zsh documentation,
but I couldn't find the answer there. I then checked
and found
" "\ddd", where ddd is a one, two, or three-digit octal number, shall
  be written as a byte with the numeric value specified by the octal
  number. "
To me, this seems to mean that it should print just a '%', instead of
converting it to '%' and rereading it, though I may well be misreading
this. (It works as I expected with coreutils's printf, by the way.)

A patch for this is a bit too much for me at the moment though, even
moreso since I'd hate to work on it when it may turn out not to be a
bug, sorry.

Thanks in advance.

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