mysqltest treats a plus sign inside an ordinary comment as a hint introducer

Source inspection of MariaDB 12.3.3 shows that a plus sign followed by an apostrophe inside an ordinary C-style comment makes mysqltest treat the apostrophe as the start of quoted text. This hides the first semicolon from delimiter processing and causes mysqltest to combine the two statements. Under --ps-protocol, the combined text is then expected to be rejected as a multi-statement prepare. This is source-supported; mysqltest itself was not available for runtime execution in the verification environment. The server-side SQL parser is not affected.

This occurs when an ordinary C-style comment contains + or ! after the comment introducer, followed by an unmatched quote-like character before the statement delimiter.

Save the following three files in an empty directory.

case.test:

SELECT 74 AS first /* arithmetic + isn't executable */;

SELECT 75 AS second;

case.result:

SELECT 74 AS first /* arithmetic + isn't executable */;

first

74

SELECT 75 AS second;

second

75

run.sh:

#!/usr/bin/env bash

set -euo pipefail

if [[ $# -ne 1 ]]; then

  echo "usage: $0 /path/to/mariadb-source" >&2

  exit 2

fi

src=$(realpath "$1")

here=$(cd "$(dirname "$0")" && pwd)

build="$here/build"

suite="$here/mysql-test/suite/comment_boundary"

mkdir -p "$build" "$suite/t" "$suite/r"

cp "$here/case.test" "$suite/t/comment_boundary.test"

cp "$here/case.result" "$suite/r/comment_boundary.result"

cmake -S "$src" -B "$build" \

  -DCMAKE_BUILD_TYPE=Debug \

  -DWITHOUT_SERVER=OFF \

  -DWITH_UNIT_TESTS=OFF

cmake --build "$build" --parallel --target mariadbd mysqltest

runner="$src/mysql-test/mariadb-test-run.pl"

common=(--mem --basedir="$build" --vardir="$here/var" --suite="$suite")

perl "$runner" "${common[@]}" comment_boundary

perl "$runner" "${common[@]}" --ps-protocol comment_boundary

With CMake, a C/C++ toolchain, Perl, and MariaDB's normal build dependencies installed, run:

chmod +x run.sh

./run.sh /path/to/mariadb-source

Correct behavior is for both invocations to exit successfully and produce first=74 and second=75 once each as separate statements. The supplied result file is the oracle for that behavior. The frozen runtime evidence only executed the same two SELECT statements through the server-side SQL interface, where they returned 74 and 75 successfully; that control does not exercise mysqltest's lexer.

In client/mysqltest.cc, mysqltest enters R_CSTYLE_COMMENT after /* but changes to R_HINT upon any later + or Unable to render embedded object: File (}}, without requiring the character to occur at the comment introducer. In this case, the apostrophe in {{isn't}} is consequently processed as a quote, so the first semicolon is not recognized as the statement delimiter. Only {{/*+}} and {{/*) not found. at the introducer should enable special-comment processing; later characters in an ordinary comment should remain lexically inert.