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Track function start and ends for flame graphs
With this patch, and this file I called `log.py`: #!/usr/bin/env nix-shell #!nix-shell -i python3 -p python3 --pure import sys from pprint import pprint stack = [] timestack = [] for line in open(sys.argv[1]): components = line.strip().split(" ", 2) if components[0] != "function-trace": continue direction = components[1] components = components[2].rsplit(" ", 2) loc = components[0] _at = components[1] time = int(components[2]) if direction == "entered": stack.append(loc) timestack.append(time) elif direction == "exited": dur = time - timestack.pop() vst = ";".join(stack) print(f"{vst} {dur}") stack.pop() and: nix-instantiate --trace-function-calls -vvvv ../nixpkgs/pkgs/top-level/release.nix -A unstable > log.matthewbauer 2>&1 ./log.py ./log.matthewbauer > log.matthewbauer.folded flamegraph.pl --title matthewbauer-post-pr log.matthewbauer.folded > log.matthewbauer.folded.svg I can make flame graphs like: http://gsc.io/log.matthewbauer.folded.svg --- Includes test cases around function call failures and tryEval. Uses RAII so the finish is always called at the end of the function.
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7 changed files with 189 additions and 3 deletions
39
contrib/stack-collapse.py
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39
contrib/stack-collapse.py
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@ -0,0 +1,39 @@
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#!/usr/bin/env nix-shell
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#!nix-shell -i python3 -p python3 --pure
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# To be used with `--trace-function-calls` and `-vvvv` and
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# `flamegraph.pl`.
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#
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# For example:
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#
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# nix-instantiate --trace-function-calls -vvvv '<nixpkgs>' -A hello 2> nix-function-calls.trace
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# ./contrib/stack-collapse.py nix-function-calls.trace > nix-function-calls.folded
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# nix-shell -p flamegraph --run "flamegraph.pl nix-function-calls.folded > nix-function-calls.svg"
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import sys
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from pprint import pprint
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import fileinput
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stack = []
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timestack = []
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for line in fileinput.input():
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components = line.strip().split(" ", 2)
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if components[0] != "function-trace":
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continue
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direction = components[1]
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components = components[2].rsplit(" ", 2)
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loc = components[0]
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_at = components[1]
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time = int(components[2])
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if direction == "entered":
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stack.append(loc)
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timestack.append(time)
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elif direction == "exited":
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dur = time - timestack.pop()
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vst = ";".join(stack)
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print(f"{vst} {dur}")
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stack.pop()
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@ -973,6 +973,34 @@ requiredSystemFeatures = [ "kvm" ];
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</varlistentry>
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<varlistentry xml:id="conf-trace-function-calls"><term><literal>trace-function-calls</literal></term>
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<listitem>
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<para>Default: <literal>false</literal>.</para>
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<para>If set to <literal>true</literal>, the Nix evaluator will
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trace every function call. Nix will print a log message at the
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"vomit" level for every function entrance and function exit.</para>
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<informalexample><screen>
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function-trace entered undefined position at 1565795816999559622
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function-trace exited undefined position at 1565795816999581277
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function-trace entered /nix/store/.../example.nix:226:41 at 1565795253249935150
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function-trace exited /nix/store/.../example.nix:226:41 at 1565795253249941684
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</screen></informalexample>
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<para>The <literal>undefined position</literal> means the function
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call is a builtin.</para>
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<para>Use the <literal>contrib/stack-collapse.py</literal> script
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distributed with the Nix source code to convert the trace logs
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in to a format suitable for <command>flamegraph.pl</command>.</para>
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</listitem>
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</varlistentry>
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<varlistentry xml:id="conf-trusted-public-keys"><term><literal>trusted-public-keys</literal></term>
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<listitem><para>A whitespace-separated list of public keys. When
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@ -9,6 +9,7 @@
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#include "json.hh"
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#include <algorithm>
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#include <chrono>
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#include <cstring>
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#include <unistd.h>
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#include <sys/time.h>
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#include <iostream>
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#include <fstream>
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#include <sys/time.h>
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#include <sys/resource.h>
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#if HAVE_BOEHMGC
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@ -1094,9 +1094,13 @@ void EvalState::callPrimOp(Value & fun, Value & arg, Value & v, const Pos & pos)
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}
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}
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void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & pos)
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{
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std::optional<FunctionCallTrace> trace;
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if (evalSettings.traceFunctionCalls) {
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trace.emplace(pos);
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}
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forceValue(fun, pos);
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if (fun.type == tPrimOp || fun.type == tPrimOpApp) {
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@ -6,6 +6,7 @@
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#include "symbol-table.hh"
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#include "hash.hh"
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#include "config.hh"
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#include "function-trace.hh"
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#include <map>
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#include <unordered_map>
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@ -349,6 +350,9 @@ struct EvalSettings : Config
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Setting<Strings> allowedUris{this, {}, "allowed-uris",
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"Prefixes of URIs that builtin functions such as fetchurl and fetchGit are allowed to fetch."};
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Setting<bool> traceFunctionCalls{this, false, "trace-function-calls",
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"Emit log messages for each function entry and exit at the 'vomit' log level (-vvvv)"};
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};
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extern EvalSettings evalSettings;
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24
src/libexpr/function-trace.hh
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24
src/libexpr/function-trace.hh
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#pragma once
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#include "eval.hh"
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#include <sys/time.h>
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namespace nix {
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struct FunctionCallTrace
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{
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const Pos & pos;
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FunctionCallTrace(const Pos & pos) : pos(pos) {
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auto duration = std::chrono::high_resolution_clock::now().time_since_epoch();
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auto ns = std::chrono::duration_cast<std::chrono::nanoseconds>(duration);
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vomit("function-trace entered %1% at %2%", pos, ns.count());
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}
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~FunctionCallTrace() {
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auto duration = std::chrono::high_resolution_clock::now().time_since_epoch();
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auto ns = std::chrono::duration_cast<std::chrono::nanoseconds>(duration);
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vomit("function-trace exited %1% at %2%", pos, ns.count());
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}
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};
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}
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86
tests/function-trace.sh
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86
tests/function-trace.sh
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source common.sh
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set +x
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expect_trace() {
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expr="$1"
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expect="$2"
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actual=$(
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nix-instantiate \
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--trace-function-calls \
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-vvvv \
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--expr "$expr" 2>&1 \
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| grep "function-trace" \
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| sed -e 's/ [0-9]*$//'
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);
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echo -n "Tracing expression '$expr'"
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set +e
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msg=$(diff -swB \
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<(echo "$expect") \
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<(echo "$actual")
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);
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result=$?
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set -e
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if [ $result -eq 0 ]; then
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echo " ok."
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else
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echo " failed. difference:"
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echo "$msg"
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return $result
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fi
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}
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# failure inside a tryEval
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expect_trace 'builtins.tryEval (throw "example")' "
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function-trace entered undefined position at
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function-trace exited undefined position at
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function-trace entered (string):1:1 at
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function-trace entered (string):1:19 at
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function-trace exited (string):1:19 at
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function-trace exited (string):1:1 at
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"
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# Missing argument to a formal function
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expect_trace '({ x }: x) { }' "
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function-trace entered undefined position at
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function-trace exited undefined position at
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function-trace entered (string):1:1 at
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function-trace exited (string):1:1 at
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"
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# Too many arguments to a formal function
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expect_trace '({ x }: x) { x = "x"; y = "y"; }' "
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function-trace entered undefined position at
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function-trace exited undefined position at
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function-trace entered (string):1:1 at
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function-trace exited (string):1:1 at
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"
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# Not enough arguments to a lambda
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expect_trace '(x: y: x + y) 1' "
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function-trace entered undefined position at
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function-trace exited undefined position at
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function-trace entered (string):1:1 at
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function-trace exited (string):1:1 at
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"
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# Too many arguments to a lambda
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expect_trace '(x: x) 1 2' "
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function-trace entered undefined position at
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function-trace exited undefined position at
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function-trace entered (string):1:1 at
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function-trace exited (string):1:1 at
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function-trace entered (string):1:1 at
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function-trace exited (string):1:1 at
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"
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# Not a function
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expect_trace '1 2' "
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function-trace entered undefined position at
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function-trace exited undefined position at
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function-trace entered (string):1:1 at
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function-trace exited (string):1:1 at
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"
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set -e
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plugins.sh \
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search.sh \
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nix-copy-ssh.sh \
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post-hook.sh
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post-hook.sh \
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function-trace.sh
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# parallel.sh
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install-tests += $(foreach x, $(nix_tests), tests/$(x))
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