cmd/internal/obj: fix Link.Diag printf errors

go1.26's vet printf checker can associate the printf-wrapper
property with local vars and struct fields if they are assigned
from a printf-like func literal (CL 706635). This leads to better
detection of mistakes.

Change-Id: I604be1e200aa1aba75e09d4f36ab68c1dba3b8a3
Reviewed-on: https://go-review.googlesource.com/c/go/+/710195
Auto-Submit: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/cmd/internal/obj/arm/asm5.go

@@ -579,7 +579,7 @@ func span5(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 		}
 
 		if int64(pc) > p.Pc {
-			ctxt.Diag("PC padding invalid: want %#d, has %#d: %v", p.Pc, pc, p)
+			ctxt.Diag("PC padding invalid: want %d, has %d: %v", p.Pc, pc, p)
 		}
 		for int64(pc) != p.Pc {
 			// emit 0xe1a00000 (MOVW R0, R0)

src/cmd/internal/obj/arm64/asm7.go

@@ -4354,7 +4354,7 @@ func (c *ctxt7) asmout(p *obj.Prog, out []uint32) (count int) {
 		// remove the NOTUSETMP flag in optab.
 		op := c.opirr(p, p.As)
 		if op&Sbit != 0 {
-			c.ctxt.Diag("can not break addition/subtraction when S bit is set", p)
+			c.ctxt.Diag("can not break addition/subtraction when S bit is set (%v)", p)
 		}
 		rt, r := p.To.Reg, p.Reg
 		if r == obj.REG_NONE {

src/cmd/internal/obj/link.go

@@ -1216,6 +1216,13 @@ type Link struct {
 	Fingerprint goobj.FingerprintType // fingerprint of symbol indices, to catch index mismatch
 }
 
+// Assert to vet's printf checker that Link.DiagFunc is a printf-like.
+func _(ctxt *Link) {
+	ctxt.DiagFunc = func(format string, args ...any) {
+		_ = fmt.Sprintf(format, args...)
+	}
+}
+
 func (ctxt *Link) Diag(format string, args ...interface{}) {
 	ctxt.Errors++
 	ctxt.DiagFunc(format, args...)

src/cmd/internal/obj/loong64/asm.go

@@ -2057,7 +2057,7 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
 
 	switch o.type_ {
 	default:
-		c.ctxt.Diag("unknown type %d %v", o.type_)
+		c.ctxt.Diag("unknown type %d", o.type_)
 		prasm(p)
 
 	case 0: // pseudo ops
@@ -4438,7 +4438,7 @@ func (c *ctxt0) specialFpMovInst(a obj.As, fclass int, tclass int) uint32 {
 		}
 	}
 
-	c.ctxt.Diag("bad class combination: %s %s,%s\n", a, fclass, tclass)
+	c.ctxt.Diag("bad class combination: %s %d,%s\n", a, fclass, tclass)
 
 	return 0
 }

src/cmd/internal/obj/mips/asm0.go

@@ -1172,7 +1172,7 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
 	}
 	switch o.type_ {
 	default:
-		c.ctxt.Diag("unknown type %d %v", o.type_)
+		c.ctxt.Diag("unknown type %d", o.type_)
 		prasm(p)
 
 	case 0: /* pseudo ops */

src/cmd/internal/obj/plist.go

@@ -63,12 +63,12 @@ func Flushplist(ctxt *Link, plist *Plist, newprog ProgAlloc) {
 			switch p.To.Sym.Name {
 			case "go_args_stackmap":
 				if p.From.Type != TYPE_CONST || p.From.Offset != abi.FUNCDATA_ArgsPointerMaps {
-					ctxt.Diag("%s: FUNCDATA use of go_args_stackmap(SB) without FUNCDATA_ArgsPointerMaps", p.Pos)
+					ctxt.Diag("%v: FUNCDATA use of go_args_stackmap(SB) without FUNCDATA_ArgsPointerMaps", p)
 				}
 				p.To.Sym = ctxt.LookupDerived(curtext, curtext.Name+".args_stackmap")
 			case "no_pointers_stackmap":
 				if p.From.Type != TYPE_CONST || p.From.Offset != abi.FUNCDATA_LocalsPointerMaps {
-					ctxt.Diag("%s: FUNCDATA use of no_pointers_stackmap(SB) without FUNCDATA_LocalsPointerMaps", p.Pos)
+					ctxt.Diag("%v: FUNCDATA use of no_pointers_stackmap(SB) without FUNCDATA_LocalsPointerMaps", p)
 				}
 				// funcdata for functions with no local variables in frame.
 				// Define two zero-length bitmaps, because the same index is used

src/cmd/internal/obj/riscv/obj.go

@@ -3026,7 +3026,7 @@ func instructionsForOpImmediate(p *obj.Prog, as obj.As, rs int16) []*instruction
 
 	low, high, err := Split32BitImmediate(ins.imm)
 	if err != nil {
-		p.Ctxt.Diag("%v: constant %d too large", p, ins.imm, err)
+		p.Ctxt.Diag("%v: constant %d too large: %v", p, ins.imm, err)
 		return nil
 	}
 	if high == 0 {