diff -up webkit-qtwebkit-23/Source/WebCore/WebCore.gyp/scripts/rule_bison.py.bison37 webkit-qtwebkit-23/Source/WebCore/WebCore.gyp/scripts/rule_bison.py
diff -up webkit-qtwebkit-23/Source/WebCore/css/makegrammar.pl.bison37 webkit-qtwebkit-23/Source/WebCore/css/makegrammar.pl
--- webkit-qtwebkit-23/Source/WebCore/css/makegrammar.pl.bison37	2014-09-24 13:42:05.000000000 +0200
+++ webkit-qtwebkit-23/Source/WebCore/css/makegrammar.pl	2020-08-31 20:06:27.333379631 +0200
@@ -73,23 +73,6 @@ if ($suffix eq ".y.in") {
 }
 
 my $fileBase = File::Spec->join($outputDir, $filename);
-system("$bison -d -p $symbolsPrefix $grammarFilePath -o $fileBase.cpp");
-
-open HEADER, ">$fileBase.h" or die;
-print HEADER << "EOF";
-#ifndef CSSGRAMMAR_H
-#define CSSGRAMMAR_H
-EOF
-
-open HPP, "<$fileBase.cpp.h" or open HPP, "<$fileBase.hpp" or die;
-while (<HPP>) {
-    print HEADER;
-}
-close HPP;
-
-print HEADER "#endif\n";
-close HEADER;
-
-unlink("$fileBase.cpp.h");
-unlink("$fileBase.hpp");
-
+my @bisonCommand = ($bison, "--defines=$fileBase.h", "-p", $symbolsPrefix, $grammarFilePath, "-o", "$fileBase.cpp");
+push @bisonCommand, "--no-lines" if $^O eq "MSWin32"; # Work around bug in bison >= 3.0 on Windows where it puts backslashes into #line directives.
+system(@bisonCommand) == 0 or die;
diff -up webkit-qtwebkit-23/Source/WebCore/DerivedSources.pri.me webkit-qtwebkit-23/Source/WebCore/DerivedSources.pri
--- webkit-qtwebkit-23/Source/WebCore/DerivedSources.pri.me	2020-08-31 21:01:11.524849986 +0200
+++ webkit-qtwebkit-23/Source/WebCore/DerivedSources.pri	2020-08-31 21:03:55.555919630 +0200
@@ -957,7 +957,7 @@ GENERATORS += stylesheets
 # GENERATOR 10: XPATH grammar
 xpathbison.output = ${QMAKE_FILE_BASE}.cpp
 xpathbison.input = XPATHBISON
-xpathbison.commands = bison -d -p xpathyy ${QMAKE_FILE_NAME} -o ${QMAKE_FUNC_FILE_OUT_PATH}/${QMAKE_FILE_BASE}.tab.c && $(MOVE) ${QMAKE_FUNC_FILE_OUT_PATH}$${QMAKE_DIR_SEP}${QMAKE_FILE_BASE}.tab.c ${QMAKE_FUNC_FILE_OUT_PATH}$${QMAKE_DIR_SEP}${QMAKE_FILE_BASE}.cpp && $(MOVE) ${QMAKE_FUNC_FILE_OUT_PATH}$${QMAKE_DIR_SEP}${QMAKE_FILE_BASE}.tab.h ${QMAKE_FUNC_FILE_OUT_PATH}$${QMAKE_DIR_SEP}${QMAKE_FILE_BASE}.h
+xpathbison.commands = bison -d -p xpathyy ${QMAKE_FILE_NAME} -o ${QMAKE_FUNC_FILE_OUT_PATH}/${QMAKE_FILE_BASE}.tab.c && cp ${QMAKE_FUNC_FILE_OUT_PATH}$${QMAKE_DIR_SEP}${QMAKE_FILE_BASE}.tab.c ${QMAKE_FUNC_FILE_OUT_PATH}$${QMAKE_DIR_SEP}${QMAKE_FILE_BASE}.cpp && cp ${QMAKE_FUNC_FILE_OUT_PATH}$${QMAKE_DIR_SEP}${QMAKE_FILE_BASE}.tab.h ${QMAKE_FUNC_FILE_OUT_PATH}$${QMAKE_DIR_SEP}${QMAKE_FILE_BASE}.h
 xpathbison.depends = ${QMAKE_FILE_NAME}
 GENERATORS += xpathbison