From e955b30872467b116d315e1682be8a82b30b8053 Mon Sep 17 00:00:00 2001
From: Ryan Gonzalez <git@refi64.dev>
Date: Sun, 20 Aug 2023 19:39:56 -0500
Subject: [PATCH] Make ALYS_BACKTRACE_TYPE=addr the default on systems with PIE
 support

alys_converter's symbolization gives much better results.
---
 README.md   | 34 ++++++++++++++++++++--------------
 src/alys.cr |  6 +++++-
 2 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/README.md b/README.md
index 6c84d2d..6b49ac3 100644
--- a/README.md
+++ b/README.md
@@ -49,28 +49,31 @@ JSON, Go pprof, folded stacks (for use with flamegraph), or a direct flamegraph
 via:
 
 ```bash
+# NOTE: passing `--symbolize` with the binary is *required* on systems where
+# ALYS_BACKTRACE_TYPE=addr by default (see below).
+
 # Outputs myfile.alys.json:
-bin/alys_converter myfile.alys
+bin/alys_converter --symbolize myprog myfile.alys
 # You can rename the output file:
-bin/alys_converter myfile.alys myfile.json
+bin/alys_converter --symbolize myprog myfile.alys myfile.json
 # and/or format & indent the JSON file:
-bin/alys_converter --indent myfile.alys
-bin/alys_converter --indent myfile.alys myfile.json
+bin/alys_converter --symbolize myprog --indent myfile.alys
+bin/alys_converter --symbolize myprog --indent myfile.alys myfile.json
 
 # Outputs myfile.pb.gz (pprof format):
-bin/alys_converter -f pprof myfile.alys
+bin/alys_converter --symbolize myprog -f pprof myfile.alys
 # You can rename the output file:
-bin/alys_converter -f pprof myfile.alys myfile.pb.gz
+bin/alys_converter --symbolize myprog -f pprof myfile.alys myfile.pb.gz
 
 # Outputs myfile.folded (folded stacks):
-bin/alys_converter -f folded-stacks myfile.alys
+bin/alys_converter --symbolize myprog -f folded-stacks myfile.alys
 # You can rename the output file:
-bin/alys_converter -f folded-stacks myfile.alys myfile.folded
+bin/alys_converter --symbolize myprog -f folded-stacks myfile.alys myfile.folded
 
 # Outputs myfile.svg (flamegraph, via inferno-flamegraph):
-bin/alys_converter -f inferno-flamegraph myfile.alys
+bin/alys_converter --symbolize myprog -f inferno-flamegraph myfile.alys
 # You can rename the output file:
-bin/alys_converter -f inferno-flamegraph myfile.alys myfile.svg
+bin/alys_converter --symbolize myprog -f inferno-flamegraph myfile.alys myfile.svg
 ```
 
 (Note that .alys files are only compatible with an identical alys_converter
@@ -179,12 +182,15 @@ via `ALYS_BACKTRACE_TYPE`:
     PIE randomizes the memory location of the executable at runtime, so it's
     impossible to know what was where after the fact.
   - `llvm-symbolizer` must be installed.
+  **This is the default on non-macOS systems.**
 - `ALYS_BACKTRACE_TYPE=name` will create backtraces that contain the function
   names but no files or line numbers. This is usually only slightly slower than
-  `ALYS_BACKTRACE_TYPE=addr` while giving enough information for proper
-  analysis, thus **this is the default value**.
-- `ALYS_BACKTRACE_TYPE=full` (the default) will create backtraces that contain
-  the function names, as well as the source file paths and line numbers.
+  `ALYS_BACKTRACE_TYPE=addr`, and it supports position-independent executables
+  on macOS, but the symbol names aren't as detailed as using `alys_converter`'s
+  symbolization.
+  **This is the default on macOS.**
+- `ALYS_BACKTRACE_TYPE=full` will create backtraces that contain the function
+  names, as well as the source file paths and line numbers.
 
 TODO: add support for & document flipping Alys on / off at runtime
 
diff --git a/src/alys.cr b/src/alys.cr
index eafd665..332f245 100644
--- a/src/alys.cr
+++ b/src/alys.cr
@@ -42,7 +42,11 @@ module Alys
     backtrace_limit : UInt32? = nil,
     sample_interval : UInt64 = 0 do
     def self.default
-      self.name
+      {% if flag?(:darwin) %}
+        self.name
+      {% else %}
+        self.addr
+      {% end %}
     end
 
     def self.none
-- 
2.45.2