On Mon, Jul 23, 2018 at 08:16:52AM +0000, Tsunakawa, Takayuki wrote: > I guess that is due to some missing files related to the libraries > listed in shared_preload_library. If so, no, because this patch > relates to failure before main().
No, I really mean a library dependency failure. For example, imagine that Postgres is compiled on Windows dynamically, and that it depends on libxml2.dll, which is itself compiled dynamically. Then imagine, in a custom build echosystem, that a folk comes in and adds lz support to libxml2 on Windows. If Postgres still consumes libxml2 but does not add in its PATH a version of lz, then a backend in need of libxml2 would fail to load, causing Postgres to not start properly. True, painful, story.
What's super fun about this is the error message. Guess which error Windows will emit? (Some paraphrasing for exact wording):
* "There was a problem starting C:\Program Files\PostgreSQL\11\bin\postgres.exe: The specified module could not be found."
* "There was a problem starting C:\Program Files\PostgreSQL\11\bin\postgres.exe: module "libxml2.dll" could not be found."
* "The program can't start because "libxml2.dll" is missing from your computer."
* "The program "C:\Program Files\PostgreSQL\11\bin\postgres.exe" can't start because an error was encountered when loading required library "C:\Program Files\PostgreSQL\11\lib\libxml.dll": libxml.dll requires "liblz.dll" but it could not be found."
Hint: not the last one.
It'll at best complain about libxml.dll being missing, despite it being very obviously present.
I had to go hunt around with Dependency Walker to figure out the actual missing DLL the last time I had to deal with this.
