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8378838: Fix issues with "dead" code elimination and serviceability agent in libjvm.so on Linux #30553

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8378838: Fix issues with "dead" code elimination and serviceability agent in libjvm.so on Linux #30553

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5 changes: 1 addition & 4 deletions make/autoconf/flags-cflags.m4
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Original file line number Diff line number Diff line change
Expand Up @@ -544,12 +544,9 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_HELPER],
TOOLCHAIN_CFLAGS_JVM="$TOOLCHAIN_CFLAGS_JVM -fstack-protector"
TOOLCHAIN_CFLAGS_JDK="-fvisibility=hidden -pipe -fstack-protector"
# reduce lib size on linux in link step, this needs also special compile flags
# do this on s390x also for libjvm (where serviceability agent is not supported)
if test "x$ENABLE_LINKTIME_GC" = xtrue; then
TOOLCHAIN_CFLAGS_JDK="$TOOLCHAIN_CFLAGS_JDK -ffunction-sections -fdata-sections"
if test "x$OPENJDK_TARGET_CPU" = xs390x && test "x$DEBUG_LEVEL" == xrelease; then
TOOLCHAIN_CFLAGS_JVM="$TOOLCHAIN_CFLAGS_JVM -ffunction-sections -fdata-sections"
fi
TOOLCHAIN_CFLAGS_JVM="$TOOLCHAIN_CFLAGS_JVM -ffunction-sections -fdata-sections"
fi
# technically NOT for CXX (but since this gives *worse* performance, use
# no-strict-aliasing everywhere!)
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13 changes: 6 additions & 7 deletions make/autoconf/flags-ldflags.m4
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
#
# Copyright (c) 2011, 2025, Oracle and/or its affiliates. All rights reserved.
# Copyright (c) 2011, 2026, Oracle and/or its affiliates. All rights reserved.
# DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
#
# This code is free software; you can redistribute it and/or modify it
Expand Down Expand Up @@ -53,16 +53,15 @@ AC_DEFUN([FLAGS_SETUP_LDFLAGS_HELPER],
# add --icf=all (Identical Code Folding — merges identical functions)
BASIC_LDFLAGS="-Wl,-z,defs -Wl,-z,relro -Wl,-z,now -Wl,--no-as-needed -Wl,--exclude-libs,ALL"

BASIC_LDFLAGS_JVM_ONLY=""
# Linux : remove unused code+data in link step
if test "x$ENABLE_LINKTIME_GC" = xtrue; then
if test "x$OPENJDK_TARGET_CPU" = xs390x; then
BASIC_LDFLAGS="$BASIC_LDFLAGS -Wl,--gc-sections"
else
BASIC_LDFLAGS_JDK_ONLY="$BASIC_LDFLAGS_JDK_ONLY -Wl,--gc-sections"
fi
# keep vtables : -Wl,--undefined-glob=_ZTV* (but this seems not to work with gold ld)
# so keep at least the Metadata vtable that is used in the serviceability agent
BASIC_LDFLAGS_JVM_ONLY="$BASIC_LDFLAGS_JVM_ONLY -Wl,--gc-sections -Wl,--undefined=_ZTV8Metadata"
BASIC_LDFLAGS_JDK_ONLY="$BASIC_LDFLAGS_JDK_ONLY -Wl,--gc-sections"
fi

BASIC_LDFLAGS_JVM_ONLY=""
LDFLAGS_LTO="-flto=auto -fuse-linker-plugin -fno-strict-aliasing $DEBUG_PREFIX_CFLAGS"

LDFLAGS_CXX_PARTIAL_LINKING="$MACHINE_FLAG -r"
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