runtime: dedup function name logic into moduledata method

For #54466.

Change-Id: I4d8e1953703b6c763e5bd53024da43efcc993489
Reviewed-on: https://go-review.googlesource.com/c/go/+/466095
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Michael Pratt <[email protected]>
Run-TryBot: Austin Clements <[email protected]>

Author: aclements

src/runtime/race.go

@@ -187,7 +187,8 @@ func raceSymbolizeCode(ctx *symbolizeCodeContext) {
 							continue
 						}
 						ctx.pc = f.Entry() + uintptr(inltree[ix].parentPc) // "caller" pc
-						ctx.fn = cfuncnameFromNameOff(fi, inltree[ix].nameOff)
+						name := funcnameFromNameOff(fi, inltree[ix].nameOff)
+						ctx.fn = &bytes(name)[0] // assume NUL-terminated
 						ctx.line = uintptr(line)
 						ctx.file = &bytes(file)[0] // assume NUL-terminated
 						ctx.off = pc - f.Entry()
@@ -197,7 +198,8 @@ func raceSymbolizeCode(ctx *symbolizeCodeContext) {
 					break
 				}
 			}
-			ctx.fn = cfuncname(fi)
+			name := funcname(fi)
+			ctx.fn = &bytes(name)[0] // assume NUL-terminated
 			ctx.line = uintptr(line)
 			ctx.file = &bytes(file)[0] // assume NUL-terminated
 			ctx.off = pc - f.Entry()

src/runtime/symtab.go

@@ -733,6 +733,14 @@ func (md *moduledata) textOff(pc uintptr) (uint32, bool) {
 	return res, true
 }
 
+// funcName returns the string at nameOff in the function name table.
+func (md *moduledata) funcName(nameOff int32) string {
+	if nameOff == 0 {
+		return ""
+	}
+	return gostringnocopy(&md.funcnametab[nameOff])
+}
+
 // FuncForPC returns a *Func describing the function that contains the
 // given program counter address, or else nil.
 //
@@ -1004,15 +1012,11 @@ func pcvalue(f funcInfo, off uint32, targetpc uintptr, cache *pcvalueCache, stri
 	return -1, 0
 }
 
-func cfuncname(f funcInfo) *byte {
-	if !f.valid() || f.nameOff == 0 {
-		return nil
-	}
-	return &f.datap.funcnametab[f.nameOff]
-}
-
 func funcname(f funcInfo) string {
-	return gostringnocopy(cfuncname(f))
+	if !f.valid() {
+		return ""
+	}
+	return f.datap.funcName(f.nameOff)
 }
 
 func funcpkgpath(f funcInfo) string {
@@ -1031,15 +1035,11 @@ func funcpkgpath(f funcInfo) string {
 	return name[:i]
 }
 
-func cfuncnameFromNameOff(f funcInfo, nameOff int32) *byte {
+func funcnameFromNameOff(f funcInfo, nameOff int32) string {
 	if !f.valid() {
-		return nil
+		return ""
 	}
-	return &f.datap.funcnametab[nameOff]
-}
-
-func funcnameFromNameOff(f funcInfo, nameOff int32) string {
-	return gostringnocopy(cfuncnameFromNameOff(f, nameOff))
+	return f.datap.funcName(nameOff)
 }
 
 func funcfile(f funcInfo, fileno int32) string {