From db4d75bb1cdb916103681f1b7138070afa638e02 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Wed, 21 Feb 2024 14:52:50 +1000
Subject: [PATCH] backtrace: use fmtlib formatters for output

---
 backtrace_stackwalk.cpp | 24 +++++++++++++++++-------
 backtrace_win32.cpp     | 30 ++++++++++++++++++++++--------
 2 files changed, 39 insertions(+), 15 deletions(-)

diff --git a/backtrace_stackwalk.cpp b/backtrace_stackwalk.cpp
index 134e98cf..def243a3 100644
--- a/backtrace_stackwalk.cpp
+++ b/backtrace_stackwalk.cpp
@@ -17,7 +17,7 @@
 #include "win32/windows.hpp"
 #include <dbghelp.h>
 
-#include <ostream>
+#include <fmt/ostream.h>
 
 using cruft::backtrace;
 
@@ -80,6 +80,17 @@ backtrace::backtrace ()
 std::ostream&
 cruft::operator<< (std::ostream &os, backtrace const &obj)
 {
+    fmt::print (os, "{}", obj);
+    return os;
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+fmt::format_context::iterator
+fmt::formatter<cruft::backtrace>::format (
+    cruft::backtrace const &obj,
+    fmt::format_context &ctx
+) {
     const auto process = GetCurrentProcess ();
 
     struct {
@@ -91,21 +102,20 @@ cruft::operator<< (std::ostream &os, backtrace const &obj)
     sym.info.SizeOfStruct = sizeof (sym.info);
     sym.info.MaxNameLen = std::size (sym.name);
 
-    os << "[ ";
+    fmt::format_to (ctx.out (), "[ ");
 
     for (auto const frame: obj.frames ()) {
-        os << "{ addr: " << frame << ", name: ";
+        fmt::format_to (ctx.out (), "{{ addr: {}, name: ", frame);
 
         // Find the symbol name
         sym.info.Name[0] = '\0';
         memset (sym.name, 0, sizeof (sym.name));
         if (FALSE == SymFromAddr (process, reinterpret_cast<uintptr_t> (frame), nullptr, &sym.info)) {
-            os << "null }, ";
+            fmt::format_to (ctx.out (), "null }}, ");
         } else {
-            os << '\'' << sym.info.Name << "' }, ";
+            fmt::format_to (ctx.out (), "'{}' }}, ", sym.info.Name);
         }
     }
 
-    os << " ]";
-    return os;
+    return fmt::format_to (ctx.out (), " ]");
 }
diff --git a/backtrace_win32.cpp b/backtrace_win32.cpp
index 22635ec3..6025a8b7 100644
--- a/backtrace_win32.cpp
+++ b/backtrace_win32.cpp
@@ -45,9 +45,11 @@ backtrace::backtrace (void)
 
 
 ///////////////////////////////////////////////////////////////////////////////
-std::ostream&
-debug::operator <<(std::ostream &os, ::cruft::backtrace const &rhs)
-{
+fmt::format_context::iterator
+fmt::formatter<cruft::backtrace>::format (
+    cruft::backtrace const &obj,
+    fmt::format_context &ctx
+) {
     static auto process = GetCurrentProcess ();
     CHECK (ready);
 
@@ -60,17 +62,29 @@ debug::operator <<(std::ostream &os, ::cruft::backtrace const &rhs)
     symbol.info.MaxNameLen   = MAX_LENGTH;
     symbol.info.SizeOfStruct = sizeof (SYMBOL_INFO);
 
-    os << "[ ";
+    fmt::format_to (ctx.out (), "[ ");
     for (void *frame: rhs.frames ()) {
         symbol.name[0] = '\0';
         SymFromAddr (process, (DWORD64)frame, 0, &symbol.info);
         symbol.name[MAX_LENGTH] = '\0';
 
-        os << "{ addr: "  << frame
-           << ", name: '" << symbol.name '\''
-           << " }, ";
+        fmt::format_to (
+            ctx.out (),
+            "{{ addr: {}, name: '{}' }}, ",
+            frame,
+            symbol.name
+        );
     }
 
-    os << " ]";
+    return fmt::format_to (ctx.out (), " ]");
+}
+
+
+
+///////////////////////////////////////////////////////////////////////////////
+std::ostream&
+debug::operator <<(std::ostream &os, ::cruft::backtrace const &rhs)
+{
+    fmt::print (os, "{}", rhs);
     return os;
 }