RFR: JDK-8198862 Stop doing funky compilation stuff for dtrace (original) (raw)

David Holmes david.holmes at oracle.com
Fri Mar 2 02:01:50 UTC 2018

Hi Magnus,

On 1/03/2018 10:48 AM, Magnus Ihse Bursie wrote:

We're doing a lot of weird compilation stuff for dtrace. With this patch, most of the weirdness is removed. The remaining calls to $(CC) -E has been changed to $(CPP) to clarify that we do not compile, we just use the precompiler.

One of the changes I made was to actually split up the last and final dtrace call into a separate preprocessing step. However, this uses the solaris studio preprocessor instead of the ancient system preprocessor, which has changed behavior. A string like (&``var) is now expanded to (& var), which is not accepted by dtrace. :-( I have worked around this by adding the preprocessed output, without the spaces, in two places. If anyone wants to dig deeper into dtrace script file syntax, or C preprocessor magic, to avoid this, let me know... (I'll just state that the "obvious" solution of sending -Xs to the preprocessor to get old-style behavior does not work: this just makes the solaris studio preprocessor call the ancient preprocessor in turn, and we've gained nothing...) Bug: https://bugs.openjdk.java.net/browse/JDK-8198862 WebRev: http://cr.openjdk.java.net/~ihse/JDK-8198862-stop-doing-funky-dtrace-compilation-stuff/webrev.01

Why did you rename generateJvmOffsetsMain.c to generateJvmOffsetsMain.cpp? It isn't a C++ program, it's just a C program.

I agree the logic is quite confusing. I think this build logic was victim of the CPP_FLAGS (meaning C preprocessor) to CXX_FLAGS (meaning C++ flags) renaming. But this is a trivial C program and should require trivial C compiler flags. I don't see it should be being built with all the JVM_CFLAGS. The latter may be harmless but it seems wrong to lump this in together with other things.

make/hotspot/lib/CompileDtracePreJvm.gmk

! # Since we cannot generated JvmOffsets.cpp as part of the gensrc step,

Comment doesn't read right.

Thanks, David

/Magnus

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