RFR: 8313889: Fix -Wconversion warnings in foreign benchmarks

[Maurizio Cimadamore]

On Mon, 7 Aug 2023 14:40:42 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> Fix these -Wconversion warnings in the foreign benchmarks:
> 
> 
> ./test/micro/org/openjdk/bench/java/lang/foreign/libQSortJNI.c: In function ‘Java_org_openjdk_bench_java_lang_foreign_QSort_jni_1qsort_1optimized’:
> ./test/micro/org/openjdk/bench/java/lang/foreign/libQSortJNI.c:59:17: warning: conversion to ‘size_t’ {aka ‘long unsigned int’} from ‘jsize’ {aka ‘int’} may change the sign of the result [-Wsign-conversion]
>    59 |     qsort(ints, length, sizeof(jint), &comparator);
>       |                 ^~~~~~
> ./test/micro/org/openjdk/bench/java/lang/foreign/libQSortJNI.c: In function ‘Java_org_openjdk_bench_java_lang_foreign_QSort_jni_1qsort_1naive’:
> ./test/micro/org/openjdk/bench/java/lang/foreign/libQSortJNI.c:87:17: warning: conversion to ‘size_t’ {aka ‘long unsigned int’} from ‘jsize’ {aka ‘int’} may change the sign of the result [-Wsign-conversion]
>    87 |     qsort(carr, length, sizeof(jint), java_cmp);
>       |
> 
> 
> In this case the issue is that we're converting from a signed type to an unsigned type. So, if the source value is negative, it will be positive after conversion.
> 
> Since the source value is a Java array length in both cases, the value can not be negative, so we simply fix this by casting to `size_t` explicitly.

Marked as reviewed by mcimadamore (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/15179#pullrequestreview-1567365160