On Tue, 14 Nov 2023 16:05:51 GMT, Roger Riggs <rri...@openjdk.org> wrote:
>> Strings, after construction, are immutable but may be constructed from >> mutable arrays of bytes, characters, or integers. >> The string constructors should guard against the effects of mutating the >> arrays during construction that might invalidate internal invariants for the >> correct behavior of operations on the resulting strings. In particular, a >> number of operations have optimizations for operations on pairs of latin1 >> strings and pairs of non-latin1 strings, while operations between latin1 and >> non-latin1 strings use a more general implementation. >> >> The changes include: >> >> - Adding a warning to each constructor with an array as an argument to >> indicate that the results are indeterminate >> if the input array is modified before the constructor returns. >> The resulting string may contain any combination of characters sampled >> from the input array. >> >> - Ensure that strings that are represented as non-latin1 contain at least >> one non-latin1 character. >> For latin1 inputs, whether the arrays contain ASCII, ISO-8859-1, UTF8, or >> another encoding decoded to latin1 the scanning and compression is unchanged. >> If a non-latin1 character is found, the string is represented as >> non-latin1 with the added verification that a non-latin1 character is >> present at the same index. >> If that character is found to be latin1, then the input array has been >> modified and the result of the scan may be incorrect. >> Though a ConcurrentModificationException could be thrown, the risk to an >> existing application of an unexpected exception should be avoided. >> Instead, the non-latin1 copy of the input is re-scanned and compressed; >> that scan determines whether the latin1 or the non-latin1 representation is >> returned. >> >> - The methods that scan for non-latin1 characters and their intrinsic >> implementations are updated to return the index of the non-latin1 character. >> >> - String construction from StringBuilder and CharSequence must also be >> guarded as their contents may be modified during construction. > > Roger Riggs has updated the pull request incrementally with one additional > commit since the last revision: > > Update PPC implementation of string_compress to return the index of the > non-latin1 char > Patch supplied by TheRealMDoerr src/hotspot/cpu/x86/macroAssembler_x86.cpp line 8617: > 8615: lea(dst, Address(dst, tmp5, Address::times_1)); > 8616: subptr(len, tmp5); > 8617: jmpb(copy_chars_loop); This cause a crash if I run with `-XX:UseAVX=3 -XX:AVX3Threshold=0`: # # A fatal error has been detected by the Java Runtime Environment: # # Internal Error (macroAssembler_x86.hpp:122), pid=3400452, tid=3400470 # guarantee(this->is8bit(imm8)) failed: Short forward jump exceeds 8-bit offset at <null>:0 # Needs to be a `jmp(copy_chars_loop)`. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/16425#discussion_r1394375402
