I wanted to resend this, tagging that there is a one-line patch included
diff --git a/editors/awk.c b/editors/awk.c
index bc95c4155..60b8276e7 100644
--- a/editors/awk.c
+++ b/editors/awk.c
@@ -1983,3 +1983,3 @@ static void fsrealloc(int size)
for (; i < maxfields; i++) {
- Fields[i].type = VF_SPECIAL;
+ Fields[i].type = VF_SPECIAL | VF_DIRTY;
Fields[i].string = NULL;
Mike
On Fri, 15 Dec 2023 at 00:07, M Rubon <rubon...@gmail.com> wrote:
>
> Busybox awk handles references to empty (not provided in the input)
> fields differently during the first line of input, as compared to
> subsequent lines.
>
> root@clean2305:~# (echo a ; echo b) | awk '$2 != 0' #wrong
> b
>
> No field $2 value is provided in the input. When awk references field
> $2 for the "a" line, it is seen to have a different behaviour than
> when it is referenced for the "b" line.
>
> Problem in BusyBox v1.36.1 embedded in OpenWrt 23.05.0
> Same problem also in 21.02 versions of OpenWrt
> Same problem in BusyBox v1.37.0.git
>
> I get the correct expected output from Ubuntu gawk and Debian mawk,
> and from my fix.
> will@dev:~$ (echo a ; echo b) | awk '$2 != 0' #correct
> a
> b
> will@dev:~/busybox$ (echo a ; echo b ) | ./busybox awk '$2 != 0' #fixed
> a
> b
>
> I built and poked into the source code at editors/awk.c The function
> fsrealloc(int size) is core to allocating, initializing, reallocating,
> and reinitializing fields, both real input line fields and imaginary
> fields that the script references but do not exist in the input.
>
> When fsrealloc() needs more field space than it has previously
> allocated, it initializes those new fields differently than how they
> are later reinitialized for the next input line. This works fine for
> fields defined in the input, like $1, but does not work the first time
> when there is no input for that field (e.g. field $99)
>
> My one-line fix simply makes the initialization and clrvar()
> reinitialization use the same value for .type. I am not sure if there
> are regression tests to run, but I have not done those.
>
> I'm not sure if I understand why clrvar() is not setting .type to a
> default constant value, but in any case I have left that untouched.
>
> I am a happy busybox user. Thank you very much for your work on the system!
>
> M
>
>
> diff --git a/editors/awk.c b/editors/awk.c
> index bc95c4155..60b8276e7 100644
> --- a/editors/awk.c
> +++ b/editors/awk.c
> @@ -1981,7 +1981,7 @@ static void fsrealloc(int size)
> /* ^^^ did Fields[] move? debug aid for L.v getting
> "upstaged" by R.v in evaluate() */
>
> for (; i < maxfields; i++) {
> - Fields[i].type = VF_SPECIAL;
> + Fields[i].type = VF_SPECIAL | VF_DIRTY;
> Fields[i].string = NULL;
> }
> }
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