From cb1a5e6713a4686d20b0c0bc5b1b184ba636749d Mon Sep 17 00:00:00 2001
From: Umberto Valleriani <umberto.valleriani@wsense.it>
Date: Wed, 23 Aug 2023 09:46:16 +0200
Subject: [PATCH 1/3] add -target flag

---
 shared/parser.go | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/shared/parser.go b/shared/parser.go
index ac098fa..0fdf682 100644
--- a/shared/parser.go
+++ b/shared/parser.go
@@ -174,6 +174,8 @@ func Parse(argList []string) ParserResult {
 		"--param":   {1, pr.defaultBinaryCallback},
 		"-aux-info": {1, pr.defaultBinaryCallback},
 
+		"-target": {1, pr.compileLinkBinaryCallback},
+
 		"--version": {0, pr.compileOnlyCallback},
 		"-v":        {0, pr.compileOnlyCallback},
 

From fa0b9ea188eb4038eb3ad378b56f7cc695b69066 Mon Sep 17 00:00:00 2001
From: Umberto Valleriani <umberto.valleriani@wsense.it>
Date: Thu, 24 Aug 2023 08:49:03 +0200
Subject: [PATCH 2/3] add `--target=ARCH` in addition to `-target ARCH`

---
 shared/parser.go | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/shared/parser.go b/shared/parser.go
index 0fdf682..5b691fa 100644
--- a/shared/parser.go
+++ b/shared/parser.go
@@ -402,6 +402,8 @@ func Parse(argList []string) ParserResult {
 		{`^.+\.(o|lo|So|so|po|a|dylib|pico|nossppico)$`, flagInfo{0, pr.objectFileCallback}}, //iam: pico and nossppico are FreeBSD
 		{`^.+\.dylib(\.\d)+$`, flagInfo{0, pr.objectFileCallback}},
 		{`^.+\.(So|so)(\.\d)+$`, flagInfo{0, pr.objectFileCallback}},
+
+        {`^--target=.+$`, flagInfo{0, pr.compileLinkUnaryCallback}},
 	}
 
 	for len(argList) > 0 {

From 2ca524bbc1f0b03ec5c661cc38cbf7a219bc3047 Mon Sep 17 00:00:00 2001
From: Umberto Valleriani <umberto.valleriani@wsense.it>
Date: Thu, 24 Aug 2023 09:03:26 +0200
Subject: [PATCH 3/3] edit readme to document cross-compilation

---
 README.md | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/README.md b/README.md
index 909000c..bd77421 100644
--- a/README.md
+++ b/README.md
@@ -272,6 +272,23 @@ This can be done by setting the `LTO_LINKING_FLAGS` to be something like
 `"-g -Wl,-plugin-opt=save-temps"` which will be appended to the flags at link time.
 This will at least preserve the bitcode files, even if `get-bc` will not be able to retrieve them for you.
 
+## Cross-compilation notes
+
+When cross-compiling a project (i.e. you pass the `--target=` or `-target` flag to the compiler), 
+you'll need to set the `GLLVM_OBJCOPY` variable to either 
+* `llvm-objcopy` to use LLVM's objcopy, which naturally supports all targets that clang does.
+* `YOUR-TARGET-TRIPLE-objcopy` to use GNU's objcopy, since `objcopy` only supports the native architecture.
+
+Example:
+```sh
+# test program
+echo 'int main() { return 0; }' > a.c 
+clang --target=aarch64-linux-gnu a.c # works
+gclang --target=aarch64-linux-gnu a.c # breaks
+GLLVM_OBJCOPY=llvm-objcopy gclang --target=aarch64-linux-gnu a.c # works
+GLLVM_OBJCOPY=aarch64-linux-gnu-objcopy gclang --target=aarch64-linux-gnu a.c # works if you have GNU's arm64 toolchain
+```
+
 ## Developer tools
 
 Debugging usually boils down to looking in the logs, maybe adding a print statement or two.