Compiling module descriptors is not reproducible?
Remi Forax
forax at univ-mlv.fr
Sat May 19 11:49:40 UTC 2018
----- Mail original -----
> De: "org openjdk" <org.openjdk at io7m.com>
> À: "jigsaw-dev" <jigsaw-dev at openjdk.java.net>
> Envoyé: Samedi 19 Mai 2018 11:18:09
> Objet: Compiling module descriptors is not reproducible?
> Hello!
Hi Mark,
>
> I've been interested for a while in making all of my software builds
> reproducible [0]. I don't think there's ever been any kind of
> written guarantee that the output of javac will be completely
> deterministic, but to date it seems like it actually has been. However,
> I was a bit disappointed today to find that the output of one of the
> builds at AdoptOpenJDK [1] seems to be inserting compiler version
> information into compiled module descriptors. It doesn't seem to be
> doing this for any other class files.
>
> Here's the output of "openjdk version 10.0.1 2018-04-17" on Linux
> (not an AdoptOpenJDK build) when compiling a module descriptor:
>
> ---
> module com.io7m.jtensors.core
> minor version: 0
> major version: 53
> flags: (0x8000) ACC_MODULE
> this_class: #1 // "module-info"
> super_class: #0
> interfaces: 0, fields: 0, methods: 0, attributes: 2
> Constant pool:
> #1 = Class #17 // "module-info"
> #2 = Utf8 SourceFile
> #3 = Utf8 module-info.java
> #4 = Utf8 Module
> #5 = Module #18 // "com.io7m.jtensors.core"
> #6 = Module #19 // "java.base"
> #7 = Module #20 // "org.immutables.value"
> #8 = Module #21 // "com.io7m.junreachable.core"
> #9 = Package #22 // com/io7m/jtensors/core/determinants
> #10 = Package #23 // com/io7m/jtensors/core/dotproducts
> #11 = Package #24 //
> com/io7m/jtensors/core/parameterized/matrices
> #12 = Package #25 //
> com/io7m/jtensors/core/parameterized/vectors
> #13 = Package #26 // com/io7m/jtensors/core/quaternions
> #14 = Package #27 //
> com/io7m/jtensors/core/unparameterized/matrices
> #15 = Package #28 //
> com/io7m/jtensors/core/unparameterized/vectors
> #16 = Package #29 // com/io7m/jtensors/core
> #17 = Utf8 module-info
> #18 = Utf8 com.io7m.jtensors.core
> #19 = Utf8 java.base
> #20 = Utf8 org.immutables.value
> #21 = Utf8 com.io7m.junreachable.core
> #22 = Utf8 com/io7m/jtensors/core/determinants
> #23 = Utf8 com/io7m/jtensors/core/dotproducts
> #24 = Utf8 com/io7m/jtensors/core/parameterized/matrices
> #25 = Utf8 com/io7m/jtensors/core/parameterized/vectors
> #26 = Utf8 com/io7m/jtensors/core/quaternions
> #27 = Utf8 com/io7m/jtensors/core/unparameterized/matrices
> #28 = Utf8 com/io7m/jtensors/core/unparameterized/vectors
> #29 = Utf8 com/io7m/jtensors/core
> {
> }
> SourceFile: "module-info.java"
> Module:
> #5,0 // "com.io7m.jtensors.core"
> #0
> 3 // requires
> #6,8000 // "java.base" ACC_MANDATED
> #0
> #7,40 // "org.immutables.value"
> ACC_STATIC_PHASE
> #0
> #8,0 // "com.io7m.junreachable.core"
> #0
> 8 // exports
> #9,0 // com/io7m/jtensors/core/determinants
> #10,0 // com/io7m/jtensors/core/dotproducts
> #11,0 //
> com/io7m/jtensors/core/parameterized/matrices
> #12,0 //
> com/io7m/jtensors/core/parameterized/vectors
> #13,0 // com/io7m/jtensors/core/quaternions
> #14,0 //
> com/io7m/jtensors/core/unparameterized/matrices
> #15,0 //
> com/io7m/jtensors/core/unparameterized/vectors
> #16,0 // com/io7m/jtensors/core
> 0 // opens
> 0 // uses
> 0 // provides
> ---
>
> Here's the same module descriptor compiled on "openjdk version
> 10-internal" on MacOS (this is actually OpenJDK 10+23):
>
> ---
> module com.io7m.jtensors.core
> minor version: 0
> major version: 53
> flags: (0x8000) ACC_MODULE
> this_class: #1 // "module-info"
> super_class: #0
> interfaces: 0, fields: 0, methods: 0, attributes: 2
> Constant pool:
> #1 = Class #18 // "module-info"
> #2 = Utf8 SourceFile
> #3 = Utf8 module-info.java
> #4 = Utf8 Module
> #5 = Module #19 // "com.io7m.jtensors.core"
> #6 = Module #20 // "java.base"
> #7 = Utf8 10-internal
> #8 = Module #21 // "org.immutables.value"
> #9 = Module #22 // "com.io7m.junreachable.core"
> #10 = Package #23 // com/io7m/jtensors/core/determinants
> #11 = Package #24 // com/io7m/jtensors/core/dotproducts
> #12 = Package #25 //
> com/io7m/jtensors/core/parameterized/matrices
> #13 = Package #26 //
> com/io7m/jtensors/core/parameterized/vectors
> #14 = Package #27 // com/io7m/jtensors/core/quaternions
> #15 = Package #28 //
> com/io7m/jtensors/core/unparameterized/matrices
> #16 = Package #29 //
> com/io7m/jtensors/core/unparameterized/vectors
> #17 = Package #30 // com/io7m/jtensors/core
> #18 = Utf8 module-info
> #19 = Utf8 com.io7m.jtensors.core
> #20 = Utf8 java.base
> #21 = Utf8 org.immutables.value
> #22 = Utf8 com.io7m.junreachable.core
> #23 = Utf8 com/io7m/jtensors/core/determinants
> #24 = Utf8 com/io7m/jtensors/core/dotproducts
> #25 = Utf8 com/io7m/jtensors/core/parameterized/matrices
> #26 = Utf8 com/io7m/jtensors/core/parameterized/vectors
> #27 = Utf8 com/io7m/jtensors/core/quaternions
> #28 = Utf8 com/io7m/jtensors/core/unparameterized/matrices
> #29 = Utf8 com/io7m/jtensors/core/unparameterized/vectors
> #30 = Utf8 com/io7m/jtensors/core
> {
> }
> SourceFile: "module-info.java"
> Module:
> #5,0 // "com.io7m.jtensors.core"
> #0
> 3 // requires
> #6,8000 // "java.base" ACC_MANDATED
> #7 // 10-internal
> #8,40 // "org.immutables.value"
> ACC_STATIC_PHASE
> #0
> #9,0 // "com.io7m.junreachable.core"
> #0
> 8 // exports
> #10,0 // com/io7m/jtensors/core/determinants
> #11,0 // com/io7m/jtensors/core/dotproducts
> #12,0 //
> com/io7m/jtensors/core/parameterized/matrices
> #13,0 //
> com/io7m/jtensors/core/parameterized/vectors
> #14,0 // com/io7m/jtensors/core/quaternions
> #15,0 //
> com/io7m/jtensors/core/unparameterized/matrices
> #16,0 //
> com/io7m/jtensors/core/unparameterized/vectors
> #17,0 // com/io7m/jtensors/core
> 0 // opens
> 0 // uses
> 0 // provides
> ---
>
> Note the insertion of the "10-internal" string as constant pool entry
> 7.
>
> Does anyone have any idea why this would happen? I'm considering filing
> a bug at the AdoptOpenJDK project, but I'd like to be sure as to
> whether or not this is actually intended behaviour by newer compilers.
> Inserting version information obviously breaks reproducibility, so it'd
> be nice if it could be turned off!
>
I think it's the opposite, by default the compiler add the version of the required module,
so the AdoptOpenJDK version does the right thing, you should have the module compiled version by default,
the real question is why the compiler of the openjdk version 10.0.1 doesn't generate the required module version.
> The sources to the above module descriptor are available [2] if anyone
> wants to try compiling this for themselves. The SHA256 of the resulting
> module-info.class should be
> e7a94b5a2788a3c5cd6d7f586e70a0f2138a2eaa0e75144b6a16e75c4b297870 if
> your compiler produces the same output as mine.
>
> [0] https://reproducible-builds.org/
> [1] https://adoptopenjdk.net/
> [2] https://github.com/io7m/jtensors
>
> --
> Mark Raynsford | http://www.io7m.com
Rémi
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