[Backtracing][WIP] Add some debug to track down problem in Linux CI.

Author: al45tair

stdlib/public/Backtracing/Backtrace.swift

@@ -492,10 +492,12 @@ public struct Backtrace: CustomStringConvertible, Sendable {
       if let match = try? mapRegex.wholeMatch(in: line) {
         let path = stripWhitespace(match.pathname)
         if match.inode == "0" || path == "" {
+          print("[A] \(line)")
           continue
         }
         guard let start = Address(match.start, radix: 16),
               let end = Address(match.end, radix: 16) else {
+          print("[B] \(line)")
           continue
         }
 
@@ -506,9 +508,13 @@ public struct Backtrace: CustomStringConvertible, Sendable {
           mappedFiles[path] = AddressRange(low: start,
                                            high: end)
         }
+      } else {
+        print("[C] \(line)")
       }
     }
 
+    print("Mapped files: \(mappedFiles)")
+
     // Look for ELF headers in the process' memory
     typealias Source = MemoryImageSource<M>
     let source = Source(with: reader)
@@ -547,6 +553,7 @@ public struct Backtrace: CustomStringConvertible, Sendable {
         var endOfText: Address = range.low
 
         if let image = try? Elf32Image(source: subSource) {
+          print("\(path) is an ELF32 image")
           theUUID = image.uuid
 
           for hdr in image.programHeaders {
@@ -556,6 +563,7 @@ public struct Backtrace: CustomStringConvertible, Sendable {
             }
           }
         } else if let image = try? Elf64Image(source: subSource) {
+          print("\(path) is an ELF64 image")
           theUUID = image.uuid
 
           for hdr in image.programHeaders {
@@ -566,6 +574,7 @@ public struct Backtrace: CustomStringConvertible, Sendable {
           }
         } else {
           // Not a valid ELF image
+          print("\(path) is not an ELF image")
           continue
         }
 

stdlib/public/Backtracing/SymbolicatedBacktrace.swift

@@ -479,6 +479,7 @@ public struct SymbolicatedBacktrace: CustomStringConvertible {
            where: { address >= $0.baseAddress
                       && address < $0.endOfText }
          ) {
+
         let relativeAddress = address - FileImageSource.Address(theImages[imageNdx].baseAddress)
         var symbol: Symbol = Symbol(imageIndex: imageNdx,
                                     imageName: theImages[imageNdx].name,

test/Backtracing/Images.swift

@@ -0,0 +1,47 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift %s -parse-as-library -g -Onone -o %t/Images
+// RUN: %target-codesign %t/Images
+// RUN: %target-run %t/Images | %FileCheck %s
+
+// UNSUPPORTED: use_os_stdlib
+// UNSUPPORTED: back_deployment_runtime
+// REQUIRES: executable_test
+// REQUIRES: backtracing
+// REQUIRES: OS=linux-gnu
+
+import _Backtracing
+
+func kablam() {
+  kerpow()
+}
+
+func kerpow() {
+  whap()
+}
+
+func whap() {
+  zonk()
+}
+
+func zonk() {
+  splat()
+}
+
+func splat() {
+  pow()
+}
+
+func pow() {
+  let images = Backtrace.captureImages()
+
+  print(images)
+
+  // CHECK: frobble
+}
+
+@main
+struct Images {
+  static func main() {
+    kablam()
+  }
+}