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Skillshub Function Call Tracing

Instrument C/C++ with -finstrument-functions for execution tracing and Perfetto visualization

install
source · Clone the upstream repo
git clone https://github.com/ComeOnOliver/skillshub
Claude Code · Install into ~/.claude/skills/
T=$(mktemp -d) && git clone --depth=1 https://github.com/ComeOnOliver/skillshub "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/gadievron/raptor/function-tracing" ~/.claude/skills/comeonoliver-skillshub-function-call-tracing && rm -rf "$T"
manifest: skills/gadievron/raptor/function-tracing/SKILL.md
source content

Function Call Tracing

Purpose

Trace all function calls in C/C++ programs with per-thread logs and Perfetto visualization.

Components

1. Instrumentation Library (trace_instrument.c)

Captures function entry/exit, writes per-thread logs.

Build:

gcc -c -fPIC trace_instrument.c -o trace_instrument.o
gcc -shared trace_instrument.o -o libtrace.so -ldl -lpthread

2. Perfetto Converter (trace_to_perfetto.cpp)

Converts logs to Chrome JSON for Perfetto UI.

Build:

g++ -O3 -std=c++17 trace_to_perfetto.cpp -o trace_to_perfetto

Usage

Step 1: Add to Build

CFLAGS += -finstrument-functions -g
LDFLAGS += -L. -ltrace -ldl -lpthread

Step 2: Build Target

make

Step 3: Run

export LD_LIBRARY_PATH=.:$LD_LIBRARY_PATH
./program
# Creates trace_<tid>.log files

Step 4: Convert to Perfetto

./trace_to_perfetto trace_*.log -o trace.json
# Open trace.json in ui.perfetto.dev

Log Format

[seq] [timestamp] [dots] [ENTRY|EXIT!] function_name
[0] [1.000000000]  [ENTRY] main
[1] [1.000050000] . [ENTRY] helper
[2] [1.000100000] . [EXIT!] helper
[3] [1.000150000]  [EXIT!] main
  • Dots indicate call depth
  • Timestamp in seconds.nanoseconds
  • One log file per thread

When User Requests Tracing

Steps

  1. Copy 
    trace_instrument.c
    and 
    trace_to_perfetto.cpp
    to project
  2. Build instrumentation library
  3. Add 
    -finstrument-functions
    to CFLAGS
  4. Add 
    -L. -ltrace -ldl -lpthread
    to LDFLAGS
  5. Build project
  6. Set 
    LD_LIBRARY_PATH
    and run
  7. Convert logs: 
    ./trace_to_perfetto trace_*.log -o trace.json
  8. Provide link to ui.perfetto.dev

Build System Detection

Makefile: Add flags conditionally

ENABLE_TRACE ?= 0
ifeq ($(ENABLE_TRACE),1)
    CFLAGS += -finstrument-functions -g
    LDFLAGS += -L. -ltrace -ldl -lpthread
endif

CMake: Add option

option(ENABLE_TRACE "Enable tracing" OFF)
if(ENABLE_TRACE)
    add_compile_options(-finstrument-functions -g)
    link_libraries(trace dl pthread)
endif()

Output

Perfetto JSON Format

Function ENTRY → "B" (begin) event Function EXIT! → "E" (end) event All threads aligned by timestamp in single file.