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perf(native): optimize Windows stack walking #2018

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perf(native): optimize Windows stack walking
jpnurmi Aug 24, 2026
3d8a3ac
Update CHANGELOG.md
jpnurmi Aug 24, 2026
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
- Wine: fix OS version detection and cross-compiling Windows builds from Linux. ([#2001](https://github.com/getsentry/sentry-native/pull/2001))
- Destroy condition variables as approriate when no longer needed. ([#2004](https://github.com/getsentry/sentry-native/pull/2004))
- Crashpad/Windows: preserve module CodeView UUIDs for minimal PDB70 records with empty PDB filenames. ([#2003](https://github.com/getsentry/sentry-native/pull/2003))
- Native/Windows: improve crash-processing performance for applications with many threads. ([#2018](https://github.com/getsentry/sentry-native/pull/2018))

## 0.16.3

Expand Down
103 changes: 56 additions & 47 deletions src/backends/native/sentry_crash_daemon.c
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,9 @@
# include <sys/stat.h>
# include <windows.h>

// Global handle for ReadProcessMemory callback and shared stack-walk session
static HANDLE g_stack_walk_process = NULL;

// Forward declaration for StackWalk64-based stack unwinding (defined later)
static size_t walk_stack_with_dbghelp(HANDLE hProcess, DWORD crashed_tid,
const CONTEXT *ctx_record, const sentry_crash_context_t *crash_ctx,
Expand Down Expand Up @@ -651,13 +654,13 @@ enrich_frame_with_module_info(
frame, "package", sentry_value_new_string(mod->name));
// Note: Do NOT set image_addr on frames - it's not present in
// minidump-derived events and may cause symbolicator issues
SENTRY_DEBUGF("Frame 0x%llx -> module %s", (unsigned long long)addr,
SENTRY_TRACEF("Frame 0x%llx -> module %s", (unsigned long long)addr,
mod->name);
return;
}
}
// No matching module found - log for debugging
SENTRY_DEBUGF("Frame 0x%llx NOT matched to any module (module_count=%u)",
SENTRY_TRACEF("Frame 0x%llx NOT matched to any module (module_count=%u)",
(unsigned long long)addr, module_count);
}

Expand Down Expand Up @@ -796,7 +799,7 @@ build_stacktrace_for_thread(
sp = SENTRY__STRIP_PAC(SENTRY__ARM64_GET_SP(thread->state.__ss));
# endif

SENTRY_DEBUGF("Thread %zu: IP=0x%llx FP=0x%llx SP=0x%llx", idx,
SENTRY_TRACEF("Thread %zu: IP=0x%llx FP=0x%llx SP=0x%llx", idx,
(unsigned long long)ip, (unsigned long long)fp,
(unsigned long long)sp);

Expand All @@ -811,7 +814,7 @@ build_stacktrace_for_thread(
if (bytes_read == (ssize_t)stack_size) {
// Stack was captured from SP upward
stack_start = sp;
SENTRY_DEBUGF(
SENTRY_TRACEF(
"Loaded stack: start=0x%llx size=%llu, FP offset "
"from SP=%lld",
(unsigned long long)stack_start,
Expand All @@ -830,7 +833,7 @@ build_stacktrace_for_thread(
SENTRY_WARNF("Failed to open stack file: %s", stack_path);
}
} else {
SENTRY_DEBUGF("No stack file for thread %zu", idx);
SENTRY_TRACEF("No stack file for thread %zu", idx);
}
}
#elif defined(SENTRY_PLATFORM_LINUX) || defined(SENTRY_PLATFORM_ANDROID)
Expand Down Expand Up @@ -874,14 +877,13 @@ build_stacktrace_for_thread(
walk_thread_id = tctx->thread_id;
}

HANDLE hProcess = OpenProcess(PROCESS_VM_READ | PROCESS_QUERY_INFORMATION,
FALSE, (DWORD)ctx->crashed_pid);
if (hProcess) {
if (g_stack_walk_process) {
sentry_frame_info_t stack_frames[MAX_STACK_FRAMES];
// Make a copy since StackWalk64 may modify the context
CONTEXT ctx_copy = *walk_context;
size_t dbghelp_frame_count = walk_stack_with_dbghelp(hProcess,
walk_thread_id, &ctx_copy, ctx, stack_frames, MAX_STACK_FRAMES);
size_t dbghelp_frame_count
= walk_stack_with_dbghelp(g_stack_walk_process, walk_thread_id,
&ctx_copy, ctx, stack_frames, MAX_STACK_FRAMES);

if (dbghelp_frame_count > 0) {
// Build sentry frames from StackWalk64 results
Expand Down Expand Up @@ -927,15 +929,8 @@ build_stacktrace_for_thread(
sentry_value_set_by_key(stacktrace, "frames", frames);
sentry_value_set_by_key(stacktrace, "registers",
build_registers_from_ctx(ctx, thread_idx));

CloseHandle(hProcess);
return stacktrace;
}

CloseHandle(hProcess);
} else {
SENTRY_WARNF("Failed to open process %d for stack walk (error %lu)",
ctx->crashed_pid, GetLastError());
}
// Fall through to add at least the IP frame below
#endif
Expand Down Expand Up @@ -969,7 +964,7 @@ build_stacktrace_for_thread(
: 0;

if (remote_count > 0) {
SENTRY_DEBUGF("Remote unwound %zu frames for thread %d",
SENTRY_TRACEF("Remote unwound %zu frames for thread %d",
remote_count, tid);

for (size_t i = 0;
Expand Down Expand Up @@ -1121,7 +1116,7 @@ build_stacktrace_for_thread(
// Frame layout: [FP+0] = saved FP, [FP+8] = return addr
if (!read_stack_value(stack_buf, stack_start, stack_size,
current_fp, &saved_fp)) {
SENTRY_DEBUGF(
SENTRY_TRACEF(
"Cannot read saved FP at 0x%llx (stack: 0x%llx - 0x%llx)",
(unsigned long long)current_fp,
(unsigned long long)stack_start,
Expand All @@ -1130,20 +1125,20 @@ build_stacktrace_for_thread(
}
if (!read_stack_value(stack_buf, stack_start, stack_size,
current_fp + sizeof(uint64_t), &return_addr)) {
SENTRY_DEBUGF("Cannot read return addr at 0x%llx",
SENTRY_TRACEF("Cannot read return addr at 0x%llx",
(unsigned long long)(current_fp + sizeof(uint64_t)));
break;
}
saved_fp = SENTRY__STRIP_PAC(saved_fp);
return_addr = SENTRY__STRIP_PAC(return_addr);

SENTRY_DEBUGF("Frame %d: FP=0x%llx saved_fp=0x%llx ret=0x%llx",
SENTRY_TRACEF("Frame %d: FP=0x%llx saved_fp=0x%llx ret=0x%llx",
walk_count, (unsigned long long)current_fp,
(unsigned long long)saved_fp, (unsigned long long)return_addr);

// Validate the return address
if (!is_valid_code_addr(return_addr)) {
SENTRY_DEBUGF("Invalid return addr 0x%llx",
SENTRY_TRACEF("Invalid return addr 0x%llx",
(unsigned long long)return_addr);
break;
}
Expand All @@ -1167,7 +1162,7 @@ build_stacktrace_for_thread(

// Check for end of chain
if (saved_fp == 0 || saved_fp == current_fp) {
SENTRY_DEBUGF(
SENTRY_TRACEF(
"End of frame chain at FP=0x%llx (saved_fp=0x%llx)",
(unsigned long long)current_fp,
(unsigned long long)saved_fp);
Expand All @@ -1176,7 +1171,7 @@ build_stacktrace_for_thread(

// Sanity check: frame pointer should increase (stack grows down)
if (saved_fp < current_fp) {
SENTRY_DEBUGF("FP went backwards: 0x%llx -> 0x%llx",
SENTRY_TRACEF("FP went backwards: 0x%llx -> 0x%llx",
(unsigned long long)current_fp,
(unsigned long long)saved_fp);
break;
Expand All @@ -1185,7 +1180,7 @@ build_stacktrace_for_thread(
current_fp = saved_fp;
}

SENTRY_DEBUGF("Unwound %d frames total", frame_count);
SENTRY_TRACEF("Unwound %d frames total", frame_count);
}

// Free stack buffer
Expand Down Expand Up @@ -1554,7 +1549,7 @@ get_sym_source(const sentry_module_info_t *mod, uint32_t mod_idx)
if (mod_bid_len && dbg_bid_len
&& (mod_bid_len != dbg_bid_len
|| memcmp(mod_bid, dbg_bid, mod_bid_len) != 0)) {
SENTRY_DEBUGF(
SENTRY_TRACEF(
"Split-debug candidate %s rejected: build-id mismatch",
candidate);
continue;
Expand Down Expand Up @@ -1796,7 +1791,7 @@ capture_modules_from_proc_maps(sentry_crash_context_t *ctx)
// Convert to little-endian GUID format for Sentry debug_id
sentry__uuid_swap_guid_bytes(mod->uuid);

SENTRY_DEBUGF("Captured module: %s base=0x%llx size=0x%llx", mod->name,
SENTRY_TRACEF("Captured module: %s base=0x%llx size=0x%llx", mod->name,
(unsigned long long)mod->base_address,
(unsigned long long)mod->size);

Expand Down Expand Up @@ -2229,7 +2224,7 @@ resolve_dsym(const sentry_module_info_t *mod, macho_sym_info_t *info)
}
if (has_uuid && !is_zero_uuid(mod->uuid)
&& memcmp(uuid, mod->uuid, 16) != 0) {
SENTRY_DEBUGF(
SENTRY_TRACEF(
"dSYM candidate %s rejected: UUID mismatch", candidate);
continue;
}
Expand Down Expand Up @@ -2354,7 +2349,7 @@ enrich_frame_with_symbol(
// the file only when its UUID matches the loaded image.
if (has_uuid && !is_zero_uuid(mod->uuid)
&& memcmp(uuid, mod->uuid, 16) != 0) {
SENTRY_DEBUGF(
SENTRY_TRACEF(
"Module file %s rejected: UUID mismatch", mod->name);
usable = 0;
slot->own.fn_starts_size = 0;
Expand Down Expand Up @@ -2415,9 +2410,6 @@ enrich_frame_with_symbol(
# include <psapi.h>
# include <tlhelp32.h>

// Global handle for ReadProcessMemory callback (set during stack walk)
static HANDLE g_stack_walk_process = NULL;

/**
* Custom read memory callback for StackWalk64 to read from crashed process
*/
Expand Down Expand Up @@ -2504,13 +2496,8 @@ walk_stack_with_dbghelp(HANDLE hProcess, DWORD crashed_tid,
}
sentry_free(path_utf8);
}

SymSetOptions(SYMOPT_UNDNAME | SYMOPT_DEFERRED_LOADS
| SYMOPT_FAIL_CRITICAL_ERRORS | SYMOPT_NO_PROMPTS);
if (!SymInitializeW(hProcess, s_sym_search_path, TRUE)) {
SENTRY_WARNF("SymInitialize failed: %lu", GetLastError());
CloseHandle(hThread);
return 0;
if (s_sym_search_path) {
SymSetSearchPathW(hProcess, s_sym_search_path);
}

CONTEXT ctx = *ctx_record;
Expand Down Expand Up @@ -2544,7 +2531,6 @@ walk_stack_with_dbghelp(HANDLE hProcess, DWORD crashed_tid,
stack_frame.AddrStack.Offset = ctx.Sp;
# else
// Unsupported architecture
SymCleanup(hProcess);
CloseHandle(hThread);
return 0;
# endif
Expand Down Expand Up @@ -2582,19 +2568,17 @@ walk_stack_with_dbghelp(HANDLE hProcess, DWORD crashed_tid,
}
}

SENTRY_DEBUGF("StackWalk64 frame %zu: 0x%llx %s", frame_count,
SENTRY_TRACEF("StackWalk64 frame %zu: 0x%llx %s", frame_count,
(unsigned long long)stack_frame.AddrPC.Offset,
frames[frame_count].symbol ? frames[frame_count].symbol : "");
frame_count++;
}

sentry_free(sym_info);

SymCleanup(hProcess);
CloseHandle(hThread);
g_stack_walk_process = NULL;

SENTRY_DEBUGF("StackWalk64 captured %zu frames", frame_count);
SENTRY_TRACEF("StackWalk64 captured %zu frames", frame_count);
return frame_count;
}

Expand Down Expand Up @@ -2776,7 +2760,7 @@ extract_pdb_info_from_process(HANDLE hProcess, uint64_t module_base,
}
}

SENTRY_DEBUGF("Extracted PDB info: age=%u, pdb=%s", *pdb_age,
SENTRY_TRACEF("Extracted PDB info: age=%u, pdb=%s", *pdb_age,
pdb_name ? pdb_name : "(null)");
return true;
}
Expand Down Expand Up @@ -2839,7 +2823,7 @@ capture_modules_from_process(sentry_crash_context_t *ctx)
extract_pdb_info_from_process(hProcess, mod->base_address, mod->uuid,
&mod->pdb_age, mod->pdb_name, sizeof(mod->pdb_name));

SENTRY_DEBUGF("Captured module: %s base=0x%llx size=0x%llx pdb_age=%u",
SENTRY_TRACEF("Captured module: %s base=0x%llx size=0x%llx pdb_age=%u",
mod->name, (unsigned long long)mod->base_address,
(unsigned long long)mod->size, mod->pdb_age);

Expand Down Expand Up @@ -2997,7 +2981,7 @@ enumerate_threads_from_process(sentry_crash_context_t *ctx)
ctx->platform.threads[thread_count].context = thread_ctx;
thread_count++;

SENTRY_DEBUGF("Captured context for thread %lu",
SENTRY_TRACEF("Captured context for thread %lu",
(unsigned long)te32.th32ThreadID);
} while (Thread32Next(hSnapshot, &te32));
}
Expand Down Expand Up @@ -3206,6 +3190,23 @@ build_native_event(const sentry_crash_context_t *ctx,
sentry_value_set_by_key(exc, "mechanism", mechanism);

// Add stacktrace to exception
#if defined(SENTRY_PLATFORM_WINDOWS)
g_stack_walk_process
= OpenProcess(PROCESS_VM_READ | PROCESS_QUERY_INFORMATION, FALSE,
(DWORD)ctx->crashed_pid);
if (g_stack_walk_process) {
SymSetOptions(SYMOPT_UNDNAME | SYMOPT_DEFERRED_LOADS
| SYMOPT_FAIL_CRITICAL_ERRORS | SYMOPT_NO_PROMPTS);
if (!SymInitializeW(g_stack_walk_process, NULL, TRUE)) {
SENTRY_WARNF("SymInitialize failed: %lu", GetLastError());
CloseHandle(g_stack_walk_process);
g_stack_walk_process = NULL;
}
} else {
SENTRY_WARNF("Failed to open process %d for stack walk (error %lu)",
ctx->crashed_pid, GetLastError());
}
#endif
sentry_value_set_by_key(exc, "stacktrace", build_stacktrace_from_ctx(ctx));

// Wrap exception in values array
Expand Down Expand Up @@ -3343,6 +3344,14 @@ build_native_event(const sentry_crash_context_t *ctx,
sentry_value_set_by_key(event, "threads", threads);
}

#if defined(SENTRY_PLATFORM_WINDOWS)
if (g_stack_walk_process) {
SymCleanup(g_stack_walk_process);
CloseHandle(g_stack_walk_process);
g_stack_walk_process = NULL;
}
#endif

// Add debug_meta with module images from crashed process
// (ctx->modules[] was captured in the signal handler of the crashed
// process)
Expand Down
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