use proper case

examples/nim_timer/nim_timer.nim

@@ -33,7 +33,7 @@ type ComplexResponse {.ffi.} = object
 # --- Constructor -----------------------------------------------------------
 # Called once from Rust. Creates the FFIContext + NimTimer.
 # Uses chronos (await sleepAsync) so the body is async.
-proc nimtimer_create*(
+proc nimtimerCreate*(
     config: TimerConfig
 ): Future[Result[NimTimer, string]] {.ffiCtor.} =
   await sleepAsync(1.milliseconds) # proves chronos is live on the FFI thread
@@ -42,7 +42,7 @@ proc nimtimer_create*(
 # --- Async method ----------------------------------------------------------
 # Waits `delayMs` milliseconds (non-blocking, on the chronos event loop)
 # then echoes the message back with a request counter.
-proc nimtimer_echo*(
+proc nimtimerEcho*(
     timer: NimTimer, req: EchoRequest
 ): Future[Result[EchoResponse, string]] {.ffi.} =
   await sleepAsync(req.delayMs.milliseconds)
@@ -51,10 +51,10 @@ proc nimtimer_echo*(
 # --- Sync method -----------------------------------------------------------
 # No await — the macro detects this and fires the callback inline,
 # without going through the request channel.
-proc nimtimer_version*(timer: NimTimer): Future[Result[string, string]] {.ffi.} =
+proc nimtimerVersion*(timer: NimTimer): Future[Result[string, string]] {.ffi.} =
   return ok("nim-timer v0.1.0")
 
-proc nimtimer_complex*(
+proc nimtimerComplex*(
     timer: NimTimer, req: ComplexRequest
 ): Future[Result[ComplexResponse, string]] {.ffi.} =
   let note = if req.note.isSome: req.note.get else: "<none>"

ffi/internal/ffi_macro.nim

@@ -10,6 +10,15 @@ when defined(ffiGenBindings):
 # String helpers used by multiple macros
 # ---------------------------------------------------------------------------
 
+proc nimNameToCExport(s: string): string =
+  ## Converts a camelCase Nim proc name to a snake_case C export name.
+  ## Leaves already-snake_case names unchanged.
+  ## e.g. "nimtimerCreate" → "nimtimer_create", "nimtimer_echo" → "nimtimer_echo"
+  for i, c in s:
+    if c.isUpperAscii() and i > 0:
+      result.add('_')
+    result.add(c.toLowerAscii())
+
 proc registerFfiTypeInfo(typeDef: NimNode): NimNode {.compileTime.} =
   ## Registers the type in ffiTypeRegistry for binding generation and returns
   ## the clean typeDef. Serialization is handled by the generic overloads in serial.nim.
@@ -657,6 +666,7 @@ macro ffi*(prc: untyped): untyped =
       raw[0 ..^ 2]
     else:
       raw
+  let cExportName = nimNameToCExport(procNameStr)
   let camelName = toCamelCase(procNameStr)
 
   # Names of generated things
@@ -808,7 +818,7 @@ macro ffi*(prc: untyped): untyped =
       pragmas = newTree(
         nnkPragma,
         ident("dynlib"),
-        ident("exportc"),
+        newTree(nnkExprColonExpr, ident("exportc"), newStrLitNode(cExportName)),
         ident("cdecl"),
         newTree(nnkExprColonExpr, ident("raises"), newTree(nnkBracket)),
       ),
@@ -839,7 +849,7 @@ macro ffi*(prc: untyped): untyped =
         retTn = $retTypeInner
       ffiProcRegistry.add(
         FFIProcMeta(
-          procName: procNameStr,
+          procName: cExportName,
           libName: currentLibName,
           kind: ffiFfiKind,
           libTypeName: $libTypeName,
@@ -937,7 +947,7 @@ macro ffi*(prc: untyped): untyped =
       pragmas = newTree(
         nnkPragma,
         ident("dynlib"),
-        ident("exportc"),
+        newTree(nnkExprColonExpr, ident("exportc"), newStrLitNode(cExportName)),
         ident("cdecl"),
         newTree(nnkExprColonExpr, ident("raises"), newTree(nnkBracket)),
       ),
@@ -968,7 +978,7 @@ macro ffi*(prc: untyped): untyped =
         retTnSync = $retTypeInnerSync
       ffiProcRegistry.add(
         FFIProcMeta(
-          procName: procNameStr,
+          procName: cExportName,
           libName: currentLibName,
           kind: ffiFfiKind,
           libTypeName: $libTypeName,
@@ -1304,6 +1314,7 @@ macro ffiCtor*(prc: untyped): untyped =
       procNameStr[0 ..^ 2]
     else:
       procNameStr
+  let cExportName = nimNameToCExport(cleanName)
   let reqTypeNameStr = toCamelCase(cleanName) & "CtorReq"
   let reqTypeName = ident(reqTypeNameStr)
 
@@ -1403,7 +1414,7 @@ macro ffiCtor*(prc: untyped): untyped =
     pragmas = newTree(
       nnkPragma,
       ident("dynlib"),
-      ident("exportc"),
+      newTree(nnkExprColonExpr, ident("exportc"), newStrLitNode(cExportName)),
       ident("cdecl"),
       newTree(nnkExprColonExpr, ident("raises"), newTree(nnkBracket)),
     ),
@@ -1424,7 +1435,7 @@ macro ffiCtor*(prc: untyped): untyped =
       ctorExtraParams.add(FFIParamMeta(name: paramNames[i], typeName: tn, isPtr: isPtr))
     ffiProcRegistry.add(
       FFIProcMeta(
-        procName: cleanName,
+        procName: cExportName,
         libName: currentLibName,
         kind: ffiCtorKind,
         libTypeName: $libTypeName,