RFR: 8299329: Assertion failure with fastdebug build when trying to use CDS without classpath

[Severin Gehwolf]

On Fri, 23 Dec 2022 17:11:28 GMT, Ashutosh Mehra <duke at openjdk.org> wrote:

> It appears longest_common_app_classpath_prefix_len() is not returning correct value when there is no file separator in the path being searched backwards. Instead of returning 0 it return 1.
> 
> In case of empty classpath, it can result in assertion failure in check_paths():
> 
> `assert(strlen(rp_array->at(i)) > (size_t)runtime_prefix_len, "sanity");`
> 
> It can also result in incorrectly validating the app classpaths if they only differ by first character. Eg:
> 
> Dump time:
>   -cp hello.jar
> Run time:
>   -cp mello.jar
> 
> This would not result in classpath mismatch!
> 
> This fix updates longest_common_app_classpath_prefix_len() to return 0 if no file separator character is found.
> 
> Signed-off-by: Ashutosh Mehra <asmehra at redhat.com>

Could we add a test for this a la `test/hotspot/jtreg/runtime/cds/appcds/WrongClasspath.java`?

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PR: https://git.openjdk.org/jdk/pull/11781