Error with const variables

[Adrian Trapletti]

Hi Maurizio

Thx for the help.

What I found out is that the issue is not jextract or the platform. It's C
vs C++ default external linkage vs default internal linkage for const
variable declarations (If you rename foo.c to foo.cpp, then the symbol
table does not contain x due to internal linkage. Only if it's declared as
"extern const int x = 4;" there is external linkage in C++). In my project
the header file is imported into a cpp file.

Best,
Adrian

*Dr. Adrian Trapletti*
CEO

*Uster Metrics GmbH  *|  Steinstrasse 9b, 8610 Uster, Switzerland
P +41 32 512 83 63  |  M +41 79 103 71 31
a.trapletti at ustermetrics.com  |  www.ustermetrics.com


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On Mon, Dec 9, 2024 at 1:07 PM Maurizio Cimadamore <
maurizio.cimadamore at oracle.com> wrote:

> Hi,
> what OS/platform are you on?
>
> I tried a small example on my Linux/x64:
>
> // foo.cconst int x = 4;
>
> Then compiled to a shared library:
>
> gcc -shared -o foo.so
>
> Then, from jshell:
>
> jshell> import java.lang.foreign.*;
>
> jshell> SymbolLookup lookup = SymbolLookup.libraryLookup("./foo.so", Arena.global());
> lookup ==> java.lang.foreign.SymbolLookup$$Lambda/0x00007f8d6705ac18 at 4459eb14
>
> jshell> lookup.findOrThrow("x");
> $3 ==> MemorySegment{ address: 0x7f8dc403c000, byteSize: 0 }
>
> So, the symbol seems to be there, which is also confirmed by objdump:
>
> foo.so:     file format elf64-x86-64
>
> DYNAMIC SYMBOL TABLE:
> 0000000000000000  w   D  *UND*    0000000000000000 __cxa_finalize
> 0000000000000000  w   D  *UND*    0000000000000000 _ITM_registerTMCloneTable
> 0000000000000000  w   D  *UND*    0000000000000000 _ITM_deregisterTMCloneTable
> 0000000000000000  w   D  *UND*    0000000000000000 __gmon_start__
> 0000000000002000 g    DO .rodata    0000000000000004 x
>
> (see last line)
>
> I’d suggest to maybe check that (a) the shared library you are using (.so
> or .dll) does contain the constant variable symbols we’re trying to lookup
> and (b) that jextract is using a correct symbol lookup (e.g. one that
> points to your library). For (b) you might want to refer this for further
> guidance:
>
>
> https://github.com/openjdk/jextract/blob/master/doc/GUIDE.md#library-loading
>
> Cheers
> Maurizio
>
> On 08/12/2024 15:38, Adrian Trapletti wrote:
>
> Hi,
>
> I run jextract on
> https://github.com/ERGO-Code/HiGHS/blob/master/src/interfaces/highs_c_api.h
> .
>
> If I use the Java bindings to access the const variables I get
> "java.lang.UnsatisfiedLinkError: unresolved symbol".
>
> For example
> ...
> long sense = kHighsObjSenseMinimize();
> ...
>
> results in
>
> java.lang.UnsatisfiedLinkError: unresolved symbol: kHighsObjSenseMinimize
> at
> com.ustermetrics.highs4j/com.ustermetrics.highs4j.bindings.highs_c_api_h.lambda$findOrThrow$0(highs_c_api_h.java:44)
> at java.base/java.util.Optional.orElseThrow(Optional.java:403)
> at
> com.ustermetrics.highs4j/com.ustermetrics.highs4j.bindings.highs_c_api_h.findOrThrow(highs_c_api_h.java:44)
> at
> com.ustermetrics.highs4j/com.ustermetrics.highs4j.bindings.highs_c_api_h$kHighsObjSenseMinimize$constants.<clinit>(highs_c_api_h.java:804)
> at
> com.ustermetrics.highs4j/com.ustermetrics.highs4j.bindings.highs_c_api_h.kHighsObjSenseMinimize(highs_c_api_h.java:834)
> at
> com.ustermetrics.highs4j/com.ustermetrics.highs4j.bindings.BindingsTest.solveLinearProgramReturnsExpectedSolution(BindingsTest.java:32)
> at java.base/java.lang.reflect.Method.invoke(Method.java:580)
> at java.base/java.util.ArrayList.forEach(ArrayList.java:1597)
> at java.base/java.util.ArrayList.forEach(ArrayList.java:1597)
>
> (https://github.com/atraplet/highs4j and run the unit tests)
>
> What do I miss here?
>
> Thx and best regards,
> Adrian
>
> *Dr. Adrian Trapletti*
> CEO
>
> *Uster Metrics GmbH  *|  Steinstrasse 9b, 8610 Uster, Switzerland
> P +41 32 512 83 63  |  M +41 79 103 71 31
> a.trapletti at ustermetrics.com  |  www.ustermetrics.com
>
>
> This email message including any attachments is confidential and may be
> privileged. It is intended solely for the use of the individual or entity
> named on this message. It is provided for informational purposes only and
> does not constitute an offer or invitation to subscribe for or purchase
> any services or products. Any form of disclosure, copying, modification
> or distribution is unauthorized. If you are not the intended recipient,
> you are requested to please notify the sender immediately and delete the
> message including any attachments from your computer system network. Email
> transmission cannot be guaranteed to be secure or error free as information
> could be modified. We therefore do not accept responsibility or liability
> as to the completeness or accuracy of the information contained in this
> message or any attachments.
>
>
>
> ​
>
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