Allow for customization under the hood.

Author: ianamason

README.md

@@ -138,6 +138,11 @@ uses `objdump` on `*nix`, and `otool` on OS X.
 Both tools then use `llvm-link` or `llvm-ar` to combine the bitcode
 files into the desired form.
 
+## Customization under the hood.
+
+You can specify the exact version of `objcopy` and `ld` that `gllvm` uses
+to manipulate tha artifacts by setting the `GLLVM_OBJCOPY` and `GLLVM_LD`
+environment variables.
 
 ## License
 

shared/compiler.go

@@ -172,10 +172,18 @@ func attachBitcodePathToObject(bcFile, objFile string) {
 		var attachCmd string
 		var attachCmdArgs []string
 		if runtime.GOOS == osDARWIN {
-			attachCmd = "ld"
+			if len(LLVMLd) > 0 {
+				attachCmd = LLVMLd
+			} else {
+				attachCmd = "ld"
+			}
 			attachCmdArgs = []string{"-r", "-keep_private_externs", objFile, "-sectcreate", DarwinSegmentName, DarwinSectionName, tmpFile.Name(), "-o", objFile}
 		} else {
-			attachCmd = "objcopy"
+			if len(LLVMObjcopy) > 0 {
+				attachCmd = LLVMObjcopy
+			} else {
+				attachCmd = "objcopy"
+			}
 			attachCmdArgs = []string{"--add-section", ELFSectionName + "=" + tmpFile.Name(), objFile}
 		}
 

shared/environment.go

@@ -76,6 +76,12 @@ var LLVMLoggingLevel string
 //LLVMLoggingFile is the path to the optional logfile (useful when configuring)
 var LLVMLoggingFile string
 
+//LLVMObjcopy is the path to the objcopy executable used to attach the bitcode on *nix.
+var LLVMObjcopy string
+
+//LLVMLd is the path to the ld executable used to attach the bitcode on OSX.
+var LLVMLd string
+
 const (
 	envpath = "LLVM_COMPILER_PATH"
 	envcc   = "LLVM_CC_NAME"
@@ -86,6 +92,9 @@ const (
 	envbc   = "WLLVM_BC_STORE"
 	envlvl  = "WLLVM_OUTPUT_LEVEL"
 	envfile = "WLLVM_OUTPUT_FILE"
+	envld = "GLLVM_LD"  //iam: we are deviating from wllvm here.
+	envobjcopy = "GLLVM_OBJCOPY"  //iam: we are deviating from wllvm here.
+	//wllvm uses a BINUTILS_TARGET_PREFIX, which seems less general.
 )
 
 func init() {
@@ -102,10 +111,12 @@ func init() {
 	LLVMLoggingLevel = os.Getenv(envlvl)
 	LLVMLoggingFile = os.Getenv(envfile)
 
+	LLVMObjcopy = os.Getenv(envobjcopy)
+	LLVMLd = os.Getenv(envld)
 }
 
 func printEnvironment() {
-	vars := []string{envpath, envcc, envcxx, envar, envlnk, envcfg, envbc, envlvl, envfile}
+	vars := []string{envpath, envcc, envcxx, envar, envlnk, envcfg, envbc, envlvl, envfile, envobjcopy, envld}
 
 	informUser("\nLiving in this environment:\n\n")
 	for _, v := range vars {