Note
This content is complicated, and the possibility that it corresponds to this content in many applications is considered to be low.
Use this as a reference only when the application cannot be executed unexpectedly during a test, etc., when creating the application (as explained below, libF3 fails to load, or a runtime error occurs due to conflicts with other libraries).
For applications that use the libraries bundled with Fujitsu Enterprise Postgres, for example, if libF1, libF2, and libF3 have the following dependencies with other applications and libraries as shown below, libF3 can be directly Please specify in the build option to link.
If you do not link directly, specify the path where libF3 is stored in LD_LIBRARY_PATH when running the application.
Otherwise, an error may occur during application execution.
Example
The assumptions for this example are:
There are the following dependencies between the application and the library.
apl1->libF1->libF2 (apl1 requires libF1 and libF1 requires libF2)
apl1->libA->libF3->libF2 (apl1 requires libA, libA requires libF3, libF3 requires libF2)
libF1, libF2, and libF3 are libraries bundled with Fujitsu Enterprise Postgres.
Generally, when loading libraries, if some libA requires libB and libB requires libC, only the DT_RUNPATH value set in libA is used to search libB, and only the DT_RUNPATH value set in libB is used to search libC.
In the figure above "When libF3 is not linked directly to apl1", the search for libF1 uses the DT_RUNPATH value set in apl1. The search for libF2 uses the DT_RUNPATH value set for libF1. Since "Fujitsu Enterprise Postgres installation directory/lib" is set in each DT_RUNPATH, libF1 and libF2 bundled with Fujitsu Enterprise Postgres can be found and loaded when searching for libF1 and libF2. .
However, searching for libF3 fails to load libF3 shipped with Fujitsu Enterprise Postgres. This is because the search for libF3 uses the DT_RUNPATH value set for libA, but libA does not have a DT_RUNPATH value.
Therefore, either libF3 cannot be found and loading of libF3 fails, or even if an unexpected libF3 is found in the machine and loaded, there is a conflict between libF2 bundled with Fujitsu Enterprise Postgres conflicts and can result in run-time errors. (The conflict here is that a symbol referenced in libF3 is not defined in libF2.)
By directly linking libF3 to the application, as shown in the figure above "When libF3 is directly linked to apl1", it is possible to use the DT_RUNPATH of the application and load the libF3 bundled with Fujitsu Enterprise Postgres. can. Alternatively, you can load libF3 shipped with Fujitsu Enterprise Postgres by setting LD_LIBRARY_PATH.
