debug/gosym: add hook to disable recovers

debug/gosym assumes throughout that bogus input means a malformed file.
That's generally true, but not when you're changing the package.
In that case, the panic usually indicates a newly introduced bug,
and seeing the panic is really useful.

Add a manually-enabled way to make panics panic.

Change-Id: I07af6c7b982c4cf61180db29f07aa63576ba7837
Reviewed-on: https://go-review.googlesource.com/c/go/+/352949
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

diff --git a/src/debug/gosym/pclntab.go b/src/debug/gosym/pclntab.go
index 555add67e30d10007bbab12074723ce29e04add8..5d65b7826ade57427deb8cbd9970c6cbf918ea85 100644 (file)
--- a/src/debug/gosym/pclntab.go
+++ b/src/debug/gosym/pclntab.go
@@ -193,10 +193,12 @@ func (t *LineTable) parsePclnTab() {
        // Error paths through this code will default the version to 1.1.
        t.version = ver11
 
-       defer func() {
-               // If we panic parsing, assume it's a Go 1.1 pclntab.
-               recover()
-       }()
+       if !disableRecover {
+               defer func() {
+                       // If we panic parsing, assume it's a Go 1.1 pclntab.
+                       recover()
+               }()
+       }
 
        // Check header: 4-byte magic, two zeros, pc quantum, pointer size.
        if len(t.Data) < 16 || t.Data[4] != 0 || t.Data[5] != 0 ||
@@ -265,9 +267,11 @@ func (t *LineTable) parsePclnTab() {
 // go12Funcs returns a slice of Funcs derived from the Go 1.2 pcln table.
 func (t *LineTable) go12Funcs() []Func {
        // Assume it is malformed and return nil on error.
-       defer func() {
-               recover()
-       }()
+       if !disableRecover {
+               defer func() {
+                       recover()
+               }()
+       }
 
        n := len(t.functab) / int(t.ptrsize) / 2
        funcs := make([]Func, n)
@@ -441,7 +445,7 @@ func (t *LineTable) findFileLine(entry uint64, filetab, linetab uint32, filenum,
 // go12PCToLine maps program counter to line number for the Go 1.2 pcln table.
 func (t *LineTable) go12PCToLine(pc uint64) (line int) {
        defer func() {
-               if recover() != nil {
+               if !disableRecover && recover() != nil {
                        line = -1
                }
        }()
@@ -458,7 +462,7 @@ func (t *LineTable) go12PCToLine(pc uint64) (line int) {
 // go12PCToFile maps program counter to file name for the Go 1.2 pcln table.
 func (t *LineTable) go12PCToFile(pc uint64) (file string) {
        defer func() {
-               if recover() != nil {
+               if !disableRecover && recover() != nil {
                        file = ""
                }
        }()
@@ -490,7 +494,7 @@ func (t *LineTable) go12PCToFile(pc uint64) (file string) {
 // go12LineToPC maps a (file, line) pair to a program counter for the Go 1.2/1.16 pcln table.
 func (t *LineTable) go12LineToPC(file string, line int) (pc uint64) {
        defer func() {
-               if recover() != nil {
+               if !disableRecover && recover() != nil {
                        pc = 0
                }
        }()
@@ -552,12 +556,18 @@ func (t *LineTable) initFileMap() {
 // Every key maps to obj. That's not a very interesting map, but it provides
 // a way for callers to obtain the list of files in the program.
 func (t *LineTable) go12MapFiles(m map[string]*Obj, obj *Obj) {
-       defer func() {
-               recover()
-       }()
+       if !disableRecover {
+               defer func() {
+                       recover()
+               }()
+       }
 
        t.initFileMap()
        for file := range t.fileMap {
                m[file] = obj
        }
 }
+
+// disableRecover causes this package not to swallow panics.
+// This is useful when making changes.
+const disableRecover = false