Re: numeric instead of string comparison with array indices that look like numbers

[Andrew J. Schorr]

Hi Ed,

Thanks for the report. I see the same issue in the master branch on
Linux:

bash-5.1$ ./gawk 'BEGIN{a["10"]; for (i in a) {if (i < 2) print i}}'

But the bug is not present in an older gawk 5.1.1ish version that I have lying
around.  So there was a regression at some point...

Regards,
Andy

On Fri, Apr 19, 2024 at 06:05:14AM -0500, Ed Morton wrote:
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: cygwin
> Compiler: gcc
> Compilation CFLAGS: -ggdb -O2 -pipe -Wall -Werror=format-security
> -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector-strong
> --param=ssp-buffer-size=4 
> -fdebug-prefix-map=/cygdrive/d/a/scallywag/gawk/gawk-5.3.0-1.x86_64/build=/usr/src/debug/gawk-5.3.0-1
>  
> -fdebug-prefix-map=/cygdrive/d/a/scallywag/gawk/gawk-5.3.0-1.x86_64/src/gawk-5.3.0=/usr/src/debug/gawk-5.3.0-1
> -DNDEBUG
> uname output: CYGWIN_NT-10.0-22631 TournaMart_2023 3.5.3-1.x86_64
> 2024-04-03 17:25 UTC x86_64 Cygwin
> Machine Type: x86_64-pc-cygwin
> 
> Gawk Version: 5.3.0
> 
> Attestation 1:
>         I have read
> https://www.gnu.org/software/gawk/manual/html_node/Bugs.html.
>         Yes
> 
> Attestation 2:
>         I have not modified the sources before building gawk.
>         True
> 
> Description:
>         gawk is [presumably] doing numeric instead of string
> comparisons when
>         using an array index (always a string) on one side of the
> comparison
>         and a number on the other. This behavior can be modified just by
>         calling `typeof()` on the array index before the comparison.
> 
> Repeat-By:
>         In the following, `"10"` is always a string and we're always
> comparing
>         `"10" < 2` but note there's no output from the second script that's
>         using a variable populated from the array index and we can cause it
>         to produce the expected output just by adding a call to `typeof()`
>         in the third script:
> 
>         1) $ awk 'BEGIN{ i="10"; if(i < 2) print i }'
>            10
>            $
> 
>         2) $ awk 'BEGIN{ a["10"]; for (i in a) { if(i < 2) print i } }'
>            $
> 
>         3) $ awk 'BEGIN{ a["10"]; for (i in a) { print typeof(i);
> if(i < 2) print i } }'
>            string
>            10
>            $