Data commit

Task/Introspection/Go/introspection.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+    "debug/elf"
+    "debug/gosym"
+    "fmt"
+    "log"
+    "math"
+    "os"
+    "runtime"
+)
+
+var bloop = -3.4
+
+func main() {
+    fmt.Println("task 1: verify version")
+    fmt.Println("   program compiled with", runtime.Version())
+
+    fmt.Println("task 2: check for presence of variable and function")
+    // inspect ELF symbol table
+    f, err := elf.Open(os.Args[0])
+    if err != nil {
+        log.Fatal(err)
+    }
+    defer f.Close()
+    symSection := f.Section(".gosymtab")
+    lineSection := f.Section(".gopclntab")
+    textSection := f.Section(".text")
+    if symSection == nil || lineSection == nil || textSection == nil {
+        log.Fatal("symbolic information not found")
+    }
+    symData, err := symSection.Data()
+    if err != nil {
+        log.Fatal(err)
+    }
+    lineData, err := lineSection.Data()
+    if err != nil {
+        log.Fatal(err)
+    }
+    table, err := gosym.NewTable(symData,
+        gosym.NewLineTable(lineData, textSection.Addr))
+    if err != nil {
+        log.Fatal("  ", err)
+    }
+    var foundBloop, foundFabs bool
+    for _, s := range table.Syms {
+        if s.Name == "main.bloop" {
+            foundBloop = true
+            fmt.Println("   bloop symbol table entry:", s)
+        } else if s.Name == "math.Abs" {
+            foundFabs = true
+            fmt.Println("   abs symbol table entry:", s)
+        }
+    }
+    if foundBloop && foundFabs {
+        fmt.Println("   bloop:     ", bloop)
+        fmt.Println("   abs(bloop): ", math.Abs(bloop))
+    }
+}