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fix(tracer): fix C/C++ dynamic tracer compile/link/crash bugs #2050

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fix(tracer): fix C/C++ dynamic tracer compile/link/crash bugs #2050

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40 changes: 35 additions & 5 deletions tests/benchmarks/resolution/tracer/native-tracer.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -197,6 +197,14 @@ trace_c_cpp() {
cp "$FIXTURE_DIR"/*.h "$TMP_DIR/" 2>/dev/null || true
cp "$FIXTURE_DIR"/*.hpp "$TMP_DIR/" 2>/dev/null || true

# Snapshot the fixture's own source files *before* trace_support.c is
# written below — trace_support.c is itself a ".c" file, so for the C
# case (ext=c) computing this glob afterward would capture it too,
# causing it to be compiled+linked twice (see #1914).
cd "$TMP_DIR"
local src_files
src_files="$(ls *."$ext" 2>/dev/null | tr '\n' ' ')"

# Create instrumentation support
cat > "$TMP_DIR/trace_support.c" <<'CTRACE'
#include <stdio.h>
Expand All @@ -222,6 +230,9 @@ typedef struct { char name[128]; char file[128]; } Frame;
static Frame call_stack[MAX_STACK];
static int stack_depth = 0;

static const char* extract_name(void* addr) __attribute__((no_instrument_function));
static const char* extract_file(void* addr) __attribute__((no_instrument_function));

static const char* extract_name(void* addr) {
Dl_info info;
if (dladdr(addr, &info) && info.dli_sname) {
Expand All @@ -239,6 +250,15 @@ static const char* extract_file(void* addr) {
return "unknown";
}

// g++ compiles this file as C++ (unlike gcc, which treats .c input as C),
// so without extern "C" these two hooks would be name-mangled and no longer
// match the unmangled __cyg_profile_func_enter/_exit symbols the compiler
// auto-inserts into every instrumented translation unit, including ones
// compiled from .cpp fixture files (see #1914).
#ifdef __cplusplus
extern "C" {
#endif

void __cyg_profile_func_enter(void* callee, void* caller)
__attribute__((no_instrument_function));
void __cyg_profile_func_exit(void* callee, void* caller)
Expand Down Expand Up @@ -279,6 +299,10 @@ void __cyg_profile_func_exit(void* callee, void* caller) {
if (stack_depth > 0) stack_depth--;
}

#ifdef __cplusplus
}
#endif

void __attribute__((destructor, no_instrument_function)) dump_trace() {
printf("{\n \"edges\": [\n");
for (int i = 0; i < edge_count; i++) {
Expand All @@ -293,18 +317,24 @@ void __attribute__((destructor, no_instrument_function)) dump_trace() {
}
CTRACE

cd "$TMP_DIR"
local src_files
src_files="$(ls *."$ext" 2>/dev/null | tr '\n' ' ')"
# trace_support.c is tracer scaffolding, not code under test, and must
# never itself be built with -finstrument-functions: g++ compiles .c
# input as C++, and instrumenting this translation unit's own compiler-
# generated bookkeeping crashes at runtime (see #1914). Compile it as a
# separate, uninstrumented object and link it against the instrumented
# fixture sources.
if ! $compiler -c trace_support.c -o trace_support.o 2>/dev/null; then

@greptile-apps greptile-apps Bot Jul 8, 2026

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P2 Since trace_support.c is always pure C scaffolding, compiling it with $compiler (which is g++ for the C++ fixture) makes g++ treat the .c file as C++, requiring the #ifdef __cplusplus guards inside the heredoc to keep the hook symbols unmangled. Forcing C compilation with -x c (or always using gcc) removes that dependency and keeps the support file's compilation language-agnostic, regardless of which compiler is selected for the fixture.

Suggested change
if ! $compiler -c trace_support.c -o trace_support.o 2>/dev/null; then
if ! $compiler -x c -c trace_support.c -o trace_support.o 2>/dev/null; then

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

Fix in Claude Code

empty_result "$compiler trace_support.c compilation failed"
fi

if [[ "$compiler" == "gcc" || "$compiler" == "cc" ]]; then
if $compiler -finstrument-functions -rdynamic -ldl $src_files trace_support.c -o traced 2>/dev/null; then
if $compiler -finstrument-functions -rdynamic -ldl $src_files trace_support.o -o traced 2>/dev/null; then
./traced 2>/dev/null || echo '{"edges":[]}'
else
empty_result "$compiler compilation failed"
fi
else
if $compiler -finstrument-functions -rdynamic $src_files trace_support.c -o traced -ldl -lstdc++ 2>/dev/null; then
if $compiler -finstrument-functions -rdynamic $src_files trace_support.o -o traced -ldl -lstdc++ 2>/dev/null; then
./traced 2>/dev/null || echo '{"edges":[]}'
else
empty_result "$compiler compilation failed"
Expand Down
8 changes: 6 additions & 2 deletions tests/benchmarks/resolution/tracer/tracer-validation.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -78,8 +78,12 @@ const SAME_FILE_THRESHOLDS: Record<string, number> = {
groovy: 0.5,

// Native — sed-injected trace support
c: 0.5,
cpp: 0.5,
// c/cpp use -finstrument-functions + dladdr() instead of sed injection,
// which can only resolve the compiled binary's own filename, never the
// originating source file — same-file recall is structurally stuck at 0%
// until that's fixed (see #2049).
c: 0.0,
cpp: 0.0,
go: 0.5,
rust: 0.5,
csharp: 0.5,
Expand Down
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