8345683: Remove special flags for files compiled for static libraries

[magicus]

For various reasons, we have added some extra flags to the compiler command line when compiling C/C++ for static libraries. This is a blocker for the goal of compiling once, linking twice for static and dynamic library. Fortunately, these extra flags are not needed.

Note that -DSTATIC_BUILD=1 is still kept, but set in SetupNativeCompilation. Going forward, this flag should only be sent to the very small set of files that actually need to know if we're creating a static or dynamic library. (But that is a future follow-up.)

The flags I removed, with rationales for removing them:

• (gcc/clang) ffunction-sections -fdata-sections: This forces the compiler to create a separate section for each and every function and data entry. The idea is that the linker can use this to get rid of dead code when creating the static library, and hence saving space. The idea is perhaps good, but it does not work. libjvm.so gets about 10% larger with these flags than without them, so they are not only useless, but actually harmful.
• (gcc/clang) -DJNIEXPORT='__attribute__((visibility(\"default\")))': This is default now anyway so it does not contribute anything.
• (microsoft)-DJNIEXPORT=: The static launcher still does not work fully on Windows. (It is an ongoing project to get it to work) However, removing this flag is an essential first step, since it otherwise removes the __declspec(dllexport) annotation, and we are hence renders us unable to lookup symbols in the static libraries. (I don't understand why this was introduced in the first place.)
• (gcc) -Xassembler -mrelax-relocations=no: This was apparently added for compatibility with "older" linkers. Unfortunately, no version was given, and the original author of the code does not remember. I can build with no ill effects without this flag, so I assume that in the years that has passed, our toolchain version increments has made this unnecessary.

There is a small risk of breakage for some old/odd gcc toolchain out there. But I can see of no other realistic way of solving this than to remove the flag, and if it breaks somewhere, we can re-introduce the flag, but with a valid GCC version number attached to it.

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Issue

• JDK-8345683: Remove special flags for files compiled for static libraries (Bug - P4)

Reviewers

• Erik Joelsson (@erikj79 - Reviewer)

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[openjdk]

@magicus This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8345683: Remove special flags for files compiled for static libraries

Reviewed-by: erikj

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At the time when this comment was updated there had been 64 new commits pushed to the master branch:

• a21d21f: 8345609: [C1] LIR Operations with one input should be implemented as LIR_Op1
• 2382a2d: 8345661: Simplify page size alignment in code heap reservation
• 076bfa6: 8345656: Move os alignment functions out of ReservedSpace
• 2826838: 8345658: WB_NMTCommitMemory redundantly records an NMT tag
• c9ec271: 8345800: Update copyright year to 2024 for serviceability in files where it was missed
• 8e0f929: 8345805: Update copyright year to 2024 for other files where it was missed
• f88c1c6: 8345773: Class-File API debug printing capability
• e88e793: 8343148: C2: Refactor uses of "PhaseValue::con() + PhaseIdealLoop::set_ctrl()" into separate method
• 1e9204f: 8345273: Fix -Wzero-as-null-pointer-constant warnings in s390 code
• c40140e: 8334581: Remove no-arg constructor BasicSliderUI()
• ... and 54 more: https://git.openjdk.org/jdk/compare/daa2ba52a3197924c34ccdd0c33703e61cdc8350...master

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[mlbridge]

Webrevs

• 00: Full (e84e3ded)

[erikj79]

• (gcc) -Xassembler -mrelax-relocations=no

I managed to dig up the reason for this and have sent a question to the original stakeholders. Please hold off until we get confirmation.

[magicus]

/integrate

[openjdk]

Going to push as commit cbab40b.
Since your change was applied there have been 75 commits pushed to the master branch:

• 08bdeed: 8345269: Fix -Wzero-as-null-pointer-constant warnings in ppc code
• e4a34e9: 8345616: Unnecessary Hashtable usage in javax.swing.text.html.parser.Element
• cce5808: 8345421: (bf) Create specific test for temporary direct buffers and the buffer size limit
• cf0e1aa: 8345335: Add excluded jdk_foreign tests to manual group
• 2c4567a: 8342651: Refactor array constant to use an array of jbyte
• 72c6daf: 8346007: Incorrect copyright header in UModLNodeIdealizationTests.java
• cc47918: 8345040: Clean up unused variables and code in generate_native_wrapper
• c34b87c: 8345659: Fix broken alignment after ReservedSpace splitting in GC code
• e294899: 8345647: Fix recent NULL usage backsliding in Shenandoah
• d381d58: 8332268: C2: Add missing optimizations for UDivI/L and UModI/L and unify the shared logic with the signed nodes
• ... and 65 more: https://git.openjdk.org/jdk/compare/daa2ba52a3197924c34ccdd0c33703e61cdc8350...master

Your commit was automatically rebased without conflicts.

[openjdk]

@magicus Pushed as commit cbab40b.

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