Add code

.gitignore

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+dwarf-relocation-golang-bug

Makefile

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+.PHONY: all test
+
+all: test
+
+testdata/repro:
+	cd testdata && make
+
+dwarf-relocation-golang-bug: main.go
+	go build
+
+test: testdata/repro dwarf-relocation-golang-bug
+	@echo
+	@echo "Running test"
+	@./test.sh

README.md

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+This is a standalone repro case for https://github.com/golang/go/issues/40879
+
+* `testdata` contains logic to build an executable `testdata/repro` that:
+    * has a `.rela.debug_ranges` section
+    * has a DWARF DIE that uses DW_AT_ranges (to force this, I used a linker script to spread the code across 2 sections at different addresses)
+* `main.go` contains logic that prints the PC ranges of `testdata/repro`
+* `test.sh` will print the PC ranges using both the Go binary, and `llvm-dwarfdump`, to highlight the difference
+* `make` will compile all binaries and run `test.sh`
+
+Note: you need `llvm` installed (for `llvm-dwarfdump`). Alternatively you can change the test.sh script to use the regular `dwarfdump`.

main.go

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+package main
+
+import (
+	"debug/elf"
+	"fmt"
+	"log"
+)
+
+func main() {
+	file, err := elf.Open("testdata/repro")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+
+	dw, err := file.DWARF()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	reader := dw.Reader()
+
+	// The first entry will be the (only) CU
+	entry, err := reader.Next()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Read PC ranges from DIE
+	ranges, err := dw.Ranges(entry)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	for i := range ranges {
+		fmt.Printf("[0x%x, 0x%x)\n", ranges[i][0], ranges[i][1])
+	}
+}

test.sh

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+#!/bin/bash -eu
+
+echo "Actual ranges:"
+llvm-dwarfdump testdata/repro --name=repro.c | grep -A2 DW_AT_ranges | tail -2 | sed 's/))/)/' | tr -d ' '
+
+echo
+echo "Ranges derived from Golang's debug/elf + debug/dwarf"
+./dwarf-relocation-golang-bug
+

testdata/.gitignore

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+repro

testdata/Makefile

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+.PHONY: all
+
+repro: repro.c repro.ld
+# The following command will likely print a warning (about a missing -T option), which should be ignored.
+# Removing the warning would require passing a fully-fledged linker script to bypass gcc's default.
+	gcc -g $^ -Wl,--emit-relocs -o $@
+

testdata/repro.c

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+__attribute__((section(".coffee_section")))
+int coffee(void) {
+    return 0;
+}
+
+int main(int argc, char *argv[]) {
+	return 0;
+}

testdata/repro.ld

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+SECTIONS
+{
+    . = 0xC0FFEE;
+    .coffee_section : {}
+}