[Patch, Fortran] PR56737 - Fixing a bug in the I/O format cache handling

[Tobias Burnus]

Tobias Burnus wrote:
> b) To copy the format string
>
> The attached patch does the latter. The current hashing algorithm 
> avoids hash collisions by checking whether the value is exactly the 
> same - and the value is given by the format string. Thus, instead of 
> copying the string when storing the format in the cache, the patch 
> copies it now before calling parse_format_list.

Re-reading what Jerry wrote, I realized that the current code disables 
format caching for strings (but not for Holleriths). With my patch, 
that's no longer required. Attached is a missed-optimization patch.

> Bootstrapped and regtested on x86-64-gnu-linux.
> OK for the trunk and the 4.6/4.7/4.8 branches?

(Or should the follow-up patch only applied to the trunk?)


BTW: Without the follow up patch, the following is a memory leak as 
parse_format_list might set format_cache_ok to false:
>     if (fmt->error)
>       {
>         format_error (dtp, NULL, fmt->error);
> +      if (format_cache_ok)
> +	free (dtp->format);

Thus, if the follow-up patch is not backported, it should be changed to 
"!is_internal_unit (dtp)", which is the initial condition for 
format_cache_ok.

Tobias
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