Add compiler flag that makes NimMain function unique.

compiler/cgen.nim

@@ -947,8 +947,16 @@ proc genFilenames(m: BModule): Rope =
   for i in 0..<m.config.m.fileInfos.len:
     result.addf("dbgRegisterFilename($1);$N", [m.config.m.fileInfos[i].projPath.makeCString])
 
+proc genHashName(m: PSym, name: string): string =
+  name & $hashProc(m)
+
+proc maybeHashMain(m: BModule, name: string): string =
+  result = name
+  if optUniqueMain in m.config.globalOptions:
+    result = m.module.genHashName(name)
+
 proc genMainProc(m: BModule) =
-  const
+  let
     # The use of a volatile function pointer to call Pre/NimMainInner
     # prevents inlining of the NimMainInner function and dependent
     # functions, which might otherwise merge their stack frames.
@@ -968,7 +976,7 @@ proc genMainProc(m: BModule) =
       "}$N$N"
 
     MainProcs =
-      "\tNimMain();$N"
+      "\t" & m.maybeHashMain("NimMain") & "();$N"
 
     MainProcsWithResult =
       MainProcs & "\treturn nim_program_result;$N"
@@ -978,7 +986,7 @@ proc genMainProc(m: BModule) =
       "}$N$N"
 
     NimMainProc =
-      "N_CDECL(static void, NimMain)(void) {$N" &
+      "N_CDECL(void, " & m.maybeHashMain("NimMain") & ")(void) {$N" &
         "\tvoid (*volatile inner)(void);$N" &
         "\tPreMain();$N" &
         "\tinner = NimMainInner;$N" &

compiler/commands.nim

@@ -246,6 +246,7 @@ proc testCompileOption*(conf: ConfigRef; switch: string, info: TLineInfo): bool
   of "compileonly", "c": result = contains(conf.globalOptions, optCompileOnly)
   of "nolinking": result = contains(conf.globalOptions, optNoLinking)
   of "nomain": result = contains(conf.globalOptions, optNoMain)
+  of "uniquemain": result = contains(conf.globalOptions, optUniqueMain)
   of "forcebuild", "f": result = contains(conf.globalOptions, optForceFullMake)
   of "warnings", "w": result = contains(conf.options, optWarns)
   of "hints": result = contains(conf.options, optHints)
@@ -416,6 +417,9 @@ proc processSwitch*(switch, arg: string, pass: TCmdLinePass, info: TLineInfo;
   of "nomain":
     expectNoArg(conf, switch, arg, pass, info)
     incl(conf.globalOptions, optNoMain)
+  of "uniquemain":
+    expectNoArg(conf, switch, arg, pass, info)
+    incl(conf.globalOptions, optUniqueMain)
   of "forcebuild", "f":
     expectNoArg(conf, switch, arg, pass, info)
     incl(conf.globalOptions, optForceFullMake)

compiler/options.nim

@@ -60,6 +60,7 @@ type                          # please make sure we have under 32 options
     optSkipUserConfigFile,    # skip the users's config file
     optSkipParentConfigFiles, # skip parent dir's config files
     optNoMain,                # do not generate a "main" proc
+    optUniqueMain,            # generate a unique name for the NimMain function
     optUseColors,             # use colors for hints, warnings, and errors
     optThreads,               # support for multi-threading
     optStdout,                # output to stdout