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6911 :: Use `prologue` and `amysql` to implement WEB API, running errors, how to solve?

• lihf8515 (orginal) [2020-10-12T05:36:09+02:00] view original

  I wrote a simple example of asynchronous Web API, based on prologue and amysql. At compile time, If you use threads：on, There will be errors when running, Error SIGSEGV：Illegal storage access.? Then the program automatically exits. When I added - d：usestd to compile, There will be no errors in the program, Since prologue is also based on httpbeast, Why is there no error in using the standard library? I put the whole project code on the github now, Let's see, Thank you very much! https://github.com/lihf8515/xcm

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• enthus1ast (orginal) [2020-10-12T07:55:47+02:00] view original

  I guess, the reason is that usestd does not use threads, but httpx (the httpbeast fork that prologue uses) does.

  As far as i understand the theadvar pragma, every thread gets its own pool variable, but my guess ist that the database connection is not correctly initialized for each thread.

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• enthus1ast (orginal) [2020-10-12T08:24:25+02:00] view original

  the docs https://nim-lang.org/docs/manual.html#threads-threadvar-pragma state that: "(Every thread local variable needs to be replicated at thread creation.)"

  So you somehow must do this:

  var foo {.threadvar.}: ref bool
  
  template fixFoo() =
    echo "define foo for: ", getThreadId()
    foo = new(bool)
    foo[] = false
  
  proc faa() {.thread.} =
    fixFoo()
    echo foo[]
  
  var th1: Thread[void]
  var th2: Thread[void]
  
  createThread(th1, faa)
  createThread(th2, faa)
  
  fixFoo()
  echo foo[]
  
  joinThreads(th1, th2)
  Run

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