Fixes 8535 (#8591)

* Goodbye postInitProc

* Give preInitProc its own scope

Avoid any conflict between the variables introduced by preInitProc and
initProc since both are codegen'd in the same function body.

* Fix codegen for global var init in emulated TLS

Fixes #8535

* Add test for #8535

* Keep a bogus stack frame around

* Remove more dead code

compiler/ccgstmts.nim

@@ -256,7 +256,15 @@ proc genSingleVar(p: BProc, a: PNode) =
     # That's why we are doing the construction inside the preInitProc.
     # genObjectInit relies on the C runtime's guarantees that
     # global variables will be initialized to zero.
-    genObjectInit(p.module.preInitProc, cpsInit, v.typ, v.loc, true)
+    var loc = v.loc
+
+    # When the native TLS is unavailable, a global thread-local variable needs
+    # one more layer of indirection in order to access the TLS block.
+    # Only do this for complex types that may need a call to `objectInit`
+    if sfThread in v.flags and emulatedThreadVars(p.config) and
+      isComplexValueType(v.typ):
+      initLocExprSingleUse(p.module.preInitProc, vn, loc)
+    genObjectInit(p.module.preInitProc, cpsInit, v.typ, loc, true)
     # Alternative construction using default constructor (which may zeromem):
     # if sfImportc notin v.flags: constructLoc(p.module.preInitProc, v.loc)
     if sfExportc in v.flags and p.module.g.generatedHeader != nil:

compiler/cgen.nim

@@ -1136,12 +1136,29 @@ proc genInitCode(m: BModule) =
     appcg(m, m.s[cfsTypeInit1], "static #TNimType $1[$2];$n",
           [m.nimTypesName, rope(m.nimTypes)])
 
+  # Give this small function its own scope
+  addf(prc, "{$N", [])
+  block:
+    # Keep a bogus frame in case the code needs one
+    add(prc, ~"\tTFrame FR_; FR_.len = 0;$N")
+
+    add(prc, genSectionStart(cpsLocals, m.config))
+    add(prc, m.preInitProc.s(cpsLocals))
+    add(prc, genSectionEnd(cpsLocals, m.config))
+
+    add(prc, genSectionStart(cpsInit, m.config))
+    add(prc, m.preInitProc.s(cpsInit))
+    add(prc, genSectionEnd(cpsInit, m.config))
+
+    add(prc, genSectionStart(cpsStmts, m.config))
+    add(prc, m.preInitProc.s(cpsStmts))
+    add(prc, genSectionEnd(cpsStmts, m.config))
+  addf(prc, "}$N", [])
+
   add(prc, initGCFrame(m.initProc))
 
   add(prc, genSectionStart(cpsLocals, m.config))
-  add(prc, m.preInitProc.s(cpsLocals))
   add(prc, m.initProc.s(cpsLocals))
-  add(prc, m.postInitProc.s(cpsLocals))
   add(prc, genSectionEnd(cpsLocals, m.config))
 
   if optStackTrace in m.initProc.options and frameDeclared notin m.flags:
@@ -1155,16 +1172,13 @@ proc genInitCode(m: BModule) =
       add(prc, ~"\tTFrame FR_; FR_.len = 0;$N")
 
   add(prc, genSectionStart(cpsInit, m.config))
-  add(prc, m.preInitProc.s(cpsInit))
   add(prc, m.initProc.s(cpsInit))
-  add(prc, m.postInitProc.s(cpsInit))
   add(prc, genSectionEnd(cpsInit, m.config))
 
   add(prc, genSectionStart(cpsStmts, m.config))
-  add(prc, m.preInitProc.s(cpsStmts))
   add(prc, m.initProc.s(cpsStmts))
-  add(prc, m.postInitProc.s(cpsStmts))
   add(prc, genSectionEnd(cpsStmts, m.config))
+
   if optStackTrace in m.initProc.options and preventStackTrace notin m.flags:
     add(prc, deinitFrame(m.initProc))
   add(prc, deinitGCFrame(m.initProc))
@@ -1210,11 +1224,6 @@ proc newPreInitProc(m: BModule): BProc =
   # little hack so that unique temporaries are generated:
   result.labels = 100_000
 
-proc newPostInitProc(m: BModule): BProc =
-  result = newProc(nil, m)
-  # little hack so that unique temporaries are generated:
-  result.labels = 200_000
-
 proc initProcOptions(m: BModule): TOptions =
   let opts = m.config.options
   if sfSystemModule in m.module.flags: opts-{optStackTrace} else: opts
@@ -1236,7 +1245,6 @@ proc rawNewModule(g: BModuleList; module: PSym, filename: string): BModule =
   result.initProc = newProc(nil, result)
   result.initProc.options = initProcOptions(result)
   result.preInitProc = newPreInitProc(result)
-  result.postInitProc = newPostInitProc(result)
   initNodeTable(result.dataCache)
   result.typeStack = @[]
   result.forwardedProcs = @[]
@@ -1247,7 +1255,6 @@ proc rawNewModule(g: BModuleList; module: PSym, filename: string): BModule =
   if sfSystemModule in module.flags:
     incl result.flags, preventStackTrace
     excl(result.preInitProc.options, optStackTrace)
-    excl(result.postInitProc.options, optStackTrace)
   let ndiName = if optCDebug in g.config.globalOptions: changeFileExt(completeCFilePath(g.config, filename), "ndi")
                 else: ""
   open(result.ndi, ndiName, g.config)
@@ -1265,7 +1272,6 @@ proc resetModule*(m: BModule) =
   m.initProc = newProc(nil, m)
   m.initProc.options = initProcOptions(m)
   m.preInitProc = newPreInitProc(m)
-  m.postInitProc = newPostInitProc(m)
   initNodeTable(m.dataCache)
   m.typeStack = @[]
   m.forwardedProcs = @[]

compiler/cgendata.nim

@@ -147,7 +147,6 @@ type
     headerFiles*: seq[string] # needed headers to include
     typeInfoMarker*: TypeCache # needed for generating type information
     initProc*: BProc          # code for init procedure
-    postInitProc*: BProc      # code to be executed after the init proc
     preInitProc*: BProc       # code executed before the init proc
     typeStack*: TTypeSeq      # used for type generation
     dataCache*: TNodeTable

tests/threads/t8535.nim

@@ -0,0 +1,16 @@
+discard """
+  output: "0"
+"""
+
+type
+  CircAlloc* [Size: static[int] , T]  =  tuple
+    baseArray           : array[Size,T]
+    index               : uint16
+
+type
+  Job = object of RootObj
+
+var foo {.threadvar.}: CircAlloc[1,Job]
+
+when isMainModule:
+  echo foo.index