# Does --debug disable/affect --release mode build?

**URL:** <https://forum.crystal-lang.org/t/does-debug-disable-affect-release-mode-build/3659>\
**Category:** Help & Support\
**Created:** [August 26, 2021, 10:10am UTC](https://forum.crystal-lang.org/t/does-debug-disable-affect-release-mode-build/3659 "2021-08-26T10:10:54Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![luislavena](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/luislavena/32/572_2.png) [@luislavena](https://forum.crystal-lang.org/u/luislavena)\
**Post date:** [August 26, 2021, 10:10am UTC](https://forum.crystal-lang.org/t/does-debug-disable-affect-release-mode-build/3659/1 "2021-08-26T10:10:54Z")

</div>

Hello folks,

Been using `--debug` with release builds in order to collect as much backtrace information when exceptions are raised.

Take the following comparing example:

```crystal
cat boom.cr
def boom
  raise "BOOM!"
end

def foo
  boom
end

foo

```

When compiled without options (`crystal build boom.cr`) here is the obtained backtrace of that exception:

```auto
./boom
Unhandled exception: BOOM! (Exception)
  from boom.cr:6:3 in 'foo'
  from /home/luis/.asdf/installs/crystal/1.1.1/share/crystal/src/crystal/once.cr:44:0 in '__crystal_main'
  from /home/luis/.asdf/installs/crystal/1.1.1/share/crystal/src/crystal/main.cr:110:5 in 'main_user_code'
  from /home/luis/.asdf/installs/crystal/1.1.1/share/crystal/src/crystal/main.cr:96:7 in 'main'
  from /home/luis/.asdf/installs/crystal/1.1.1/share/crystal/src/crystal/main.cr:119:3 in 'main'
  from __libc_start_main
  from _start
  from ???

```

This is similar to adding `--debug` option, but `--release` produces something different:

```auto
./boom
Unhandled exception: BOOM! (Exception)
  from boom.cr:2:3 in 'boom'
  from boom.cr:6:3 in 'foo'
  from /home/luis/.asdf/installs/crystal/1.1.1/share/crystal/src/string.cr:252:13 in '__crystal_main'
  from __libc_start_main
  from _start
  from ???

```

And combining both `--release` and `--debug`, produces the following:

```auto
./boom
Unhandled exception: BOOM! (Exception)
  from boom.cr:2:3 in 'boom'
  from boom.cr:6:3 in 'foo'
  from /home/luis/.asdf/installs/crystal/1.1.1/share/crystal/src/crystal/once.cr:44:0 in '__crystal_main'
  from /home/luis/.asdf/installs/crystal/1.1.1/share/crystal/src/crystal/main.cr:110:5 in 'main_user_code'
  from /home/luis/.asdf/installs/crystal/1.1.1/share/crystal/src/crystal/main.cr:96:7 in 'main'
  from /home/luis/.asdf/installs/crystal/1.1.1/share/crystal/src/crystal/main.cr:119:3 in 'main'
  from __libc_start_main
  from _start
  from ???

```

However, while this has provided me a rich and accurate backtraces, it also introduced some performance issues.

Take the following HTTP server program:

```crystal
require "http/server"

server = HTTP::Server.new do |context|
  context.response.content_type = "text/plain"
  context.response.print "Hello world!"
end

Signal::INT.trap do
  puts "Shutdown requested."
  server.close
end

server.bind_tcp "0.0.0.0", 8080

puts "Listening on:"
server.addresses.each do |addr|
  puts "- #{addr}"
end
puts "Use Ctrl-C to stop"

server.listen

```

When compiled with just `--release` mode, it shows the following when performing some synthetic benchmarks:

```auto
$ plow -c 5 -d 30s http://localhost:8080/
Benchmarking http://localhost:8080/ for 30s using 5 connection(s).
@ Real-time charts is listening on http://127.0.0.1:18888/

Summary:
  Elapsed 30s
  Count 1064809
    2xx 1064809
  RPS 35492.713
  Reads 3.419MB/s
  Writes 1.963MB/s

Statistics Min Mean StdDev Max
  Latency 18µs 136µs 96µs 11.184ms
  RPS 32672.67 35492.35 787.3 36242.86

Latency Percentile:
  P50 P75 P90 P95 P99 P99.9 P99.99
  127µs 167µs 204µs 230µs 309µs 1.546ms 1.97ms

Latency Histogram:
  120µs 868738 81.59%
  184µs 165186 15.51%
  249µs 24780 2.33%
  407µs 4904 0.46%
  1.317ms 758 0.07%
  1.838ms 427 0.04%
  1.989ms 13 0.00%
  2.743ms 3 0.00%

```

Versus the exact same program build with `--release --debug` shows a ~30% slowdown:

```auto
$ plow -c 5 -d 30s http://localhost:8080/
Benchmarking http://localhost:8080/ for 30s using 5 connection(s).
@ Real-time charts is listening on http://127.0.0.1:18888/

Summary:
  Elapsed 30s
  Count 647954
    2xx 647954
  RPS 21597.793
  Reads 2.080MB/s
  Writes 1.195MB/s

Statistics Min Mean StdDev Max
  Latency 33µs 223µs 104µs 3.604ms
  RPS 20597.5 21597.24 345.18 22196.03

Latency Percentile:
  P50 P75 P90 P95 P99 P99.9 P99.99
  211µs 265µs 320µs 356µs 453µs 1.641ms 2.182ms

Latency Histogram:
  204µs 518839 80.07%
  260µs 83098 12.82%
  325µs 35479 5.48%
  417µs 9054 1.40%
  789µs 1097 0.17%
  1.574ms 267 0.04%
  1.831ms 95 0.01%
  2.17ms 25 0.00%

```

Only references I could find about debug symbols were around [this issue](https://github.com/crystal-lang/crystal/issues/10322) and [this PR](https://github.com/crystal-lang/crystal/pull/10326) associated with DWARF symbols.

Thoughts or recommendations?

Cheers,  
Luis