From 023dbb188dda6aa49ccc41c8e38f2703700b3f5a Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <iant@golang.org>
Date: Fri, 7 Sep 2018 12:53:52 -0700
Subject: [PATCH] cmd/link: don't pass all linker args when testing flag

Some linker flags can actually be input files, which can cause
misleading errors when doing the trial link, which can cause the
linker to incorrectly decide that the flag is not supported, which can
cause the link to fail.

Fixes #27510
Updates #27110
Updates #27293

Change-Id: I70c1e913cee3c813e7b267bf779bcff26d4d194a
Reviewed-on: https://go-review.googlesource.com/134057
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Damien Neil <dneil@google.com>
---
 src/cmd/link/internal/ld/lib.go  | 53 ++++++++++++++++++++++++++++++--
 src/cmd/link/internal/ld/util.go | 10 ++++++
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index 60124e3212..7029ba19c6 100644
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -1379,9 +1379,58 @@ func linkerFlagSupported(linker, flag string) bool {
 		}
 	})
 
+	flagsWithNextArgSkip := []string{
+		"-F",
+		"-l",
+		"-L",
+		"-framework",
+		"-Wl,-framework",
+		"-Wl,-rpath",
+		"-Wl,-undefined",
+	}
+	flagsWithNextArgKeep := []string{
+		"-arch",
+		"-isysroot",
+		"--sysroot",
+		"-target",
+	}
+	prefixesToKeep := []string{
+		"-f",
+		"-m",
+		"-p",
+		"-Wl,",
+		"-arch",
+		"-isysroot",
+		"--sysroot",
+		"-target",
+	}
+
 	var flags []string
-	flags = append(flags, ldflag...)
-	flags = append(flags, strings.Fields(*flagExtldflags)...)
+	keep := false
+	skip := false
+	extldflags := strings.Fields(*flagExtldflags)
+	for _, f := range append(extldflags, ldflag...) {
+		if keep {
+			flags = append(flags, f)
+			keep = false
+		} else if skip {
+			skip = false
+		} else if f == "" || f[0] != '-' {
+		} else if contains(flagsWithNextArgSkip, f) {
+			skip = true
+		} else if contains(flagsWithNextArgKeep, f) {
+			flags = append(flags, f)
+			keep = true
+		} else {
+			for _, p := range prefixesToKeep {
+				if strings.HasPrefix(f, p) {
+					flags = append(flags, f)
+					break
+				}
+			}
+		}
+	}
+
 	flags = append(flags, flag, "trivial.c")
 
 	cmd := exec.Command(linker, flags...)
diff --git a/src/cmd/link/internal/ld/util.go b/src/cmd/link/internal/ld/util.go
index b80e6106ba..b5b02296a1 100644
--- a/src/cmd/link/internal/ld/util.go
+++ b/src/cmd/link/internal/ld/util.go
@@ -89,3 +89,13 @@ var start = time.Now()
 func elapsed() float64 {
 	return time.Since(start).Seconds()
 }
+
+// contains reports whether v is in s.
+func contains(s []string, v string) bool {
+	for _, x := range s {
+		if x == v {
+			return true
+		}
+	}
+	return false
+}
-- 
2.50.0