src/win32/w32_crtdbg_stacktrace.c

/*
 * Copyright (C) the libgit2 contributors. All rights reserved.
 *
 * This file is part of libgit2, distributed under the GNU GPL v2 with
 * a Linking Exception. For full terms see the included COPYING file.
 */

#if defined(GIT_MSVC_CRTDBG)
#include "w32_stack.h"
#include "w32_crtdbg_stacktrace.h"

#define CRTDBG_STACKTRACE__UID_LEN (15)

/**
 * The stacktrace of an allocation can be distilled
 * to a unique id based upon the stackframe pointers
 * and ignoring any size arguments. We will use these
 * UIDs as the (char const*) __FILE__ argument we
 * give to the CRT malloc routines.
 */
typedef struct {
	char uid[CRTDBG_STACKTRACE__UID_LEN + 1];
} git_win32__crtdbg_stacktrace__uid;

/**
 * All mallocs with the same stacktrace will be de-duped
 * and aggregated into this row.
 */
typedef struct {
	git_win32__crtdbg_stacktrace__uid uid; /* must be first */
	git_win32__stack__raw_data raw_data;
	unsigned int count_allocs; /* times this alloc signature seen since init */
	unsigned int count_allocs_at_last_checkpoint; /* times since last mark */
	unsigned int transient_count_leaks; /* sum of leaks */
} git_win32__crtdbg_stacktrace__row;

static CRITICAL_SECTION g_crtdbg_stacktrace_cs;

/**
 * CRTDBG memory leak tracking takes a "char const * const file_name"
 * and stores the pointer in the heap data (instead of allocing a copy
 * for itself).  Normally, this is not a problem, since we usually pass
 * in __FILE__.  But I'm going to lie to it and pass in the address of
 * the UID in place of the file_name.  Also, I do not want to alloc the
 * stacktrace data (because we are called from inside our alloc routines).
 * Therefore, I'm creating a very large static pool array to store row
 * data. This also eliminates the temptation to realloc it (and move the
 * UID pointers).
 *
 * And to efficiently look for duplicates we need an index on the rows
 * so we can bsearch it.  Again, without mallocing.
 *
 * If we observe more than MY_ROW_LIMIT unique malloc signatures, we
 * fall through and use the traditional __FILE__ processing and don't
 * try to de-dup them.  If your testing hits this limit, just increase
 * it and try again.
 */

#define MY_ROW_LIMIT (1024 * 1024)
static git_win32__crtdbg_stacktrace__row  g_cs_rows[MY_ROW_LIMIT];
static git_win32__crtdbg_stacktrace__row *g_cs_index[MY_ROW_LIMIT];

static unsigned int g_cs_end = MY_ROW_LIMIT;
static unsigned int g_cs_ins = 0; /* insertion point == unique allocs seen */
static unsigned int g_count_total_allocs = 0; /* number of allocs seen */
static unsigned int g_transient_count_total_leaks = 0; /* number of total leaks */
static unsigned int g_transient_count_dedup_leaks = 0; /* number of unique leaks */
static bool g_limit_reached = false; /* had allocs after we filled row table */

static unsigned int g_checkpoint_id = 0; /* to better label leak checkpoints */
static bool g_transient_leaks_since_mark = false; /* payload for hook */

/**
 * Compare function for bsearch on g_cs_index table.
 */
static int row_cmp(const void *v1, const void *v2)
{
	git_win32__stack__raw_data *d1 = (git_win32__stack__raw_data*)v1;
	git_win32__crtdbg_stacktrace__row *r2 = (git_win32__crtdbg_stacktrace__row *)v2;

	return (git_win32__stack_compare(d1, &r2->raw_data));
}

/**
 * Unique insert the new data into the row and index tables.
 * We have to sort by the stackframe data itself, not the uid.
 */
static git_win32__crtdbg_stacktrace__row * insert_unique(
	const git_win32__stack__raw_data *pdata)
{
	size_t pos;
	if (git__bsearch(g_cs_index, g_cs_ins, pdata, row_cmp, &pos) < 0) {
		/* Append new unique item to row table. */
		memcpy(&g_cs_rows[g_cs_ins].raw_data, pdata, sizeof(*pdata));
		sprintf(g_cs_rows[g_cs_ins].uid.uid, "##%08lx", g_cs_ins);

		/* Insert pointer to it into the proper place in the index table. */
		if (pos < g_cs_ins)
			memmove(&g_cs_index[pos+1], &g_cs_index[pos], (g_cs_ins - pos)*sizeof(g_cs_index[0]));
		g_cs_index[pos] = &g_cs_rows[g_cs_ins];

		g_cs_ins++;
	}

	g_cs_index[pos]->count_allocs++;

	return g_cs_index[pos];
}

/**
 * Hook function to receive leak data from the CRT. (This includes
 * both "<file_name>:(<line_number>)" data, but also each of the
 * various headers and fields.
 *
 * Scan this for the special "##<pos>" UID forms that we substituted
 * for the "<file_name>".  Map <pos> back to the row data and
 * increment its leak count.
 *
 * See https://msdn.microsoft.com/en-us/library/74kabxyx.aspx
 *
 * We suppress the actual crtdbg output.
 */
static int __cdecl report_hook(int nRptType, char *szMsg, int *retVal)
{
	static int hook_result = TRUE; /* FALSE to get stock dump; TRUE to suppress. */
	unsigned int pos;

	*retVal = 0; /* do not invoke debugger */

	if ((szMsg[0] != '#') || (szMsg[1] != '#'))
		return hook_result;

	if (sscanf(&szMsg[2], "%08lx", &pos) < 1)
		return hook_result;
	if (pos >= g_cs_ins)
		return hook_result;

	if (g_transient_leaks_since_mark) {
		if (g_cs_rows[pos].count_allocs == g_cs_rows[pos].count_allocs_at_last_checkpoint)
			return hook_result;
	}

	g_cs_rows[pos].transient_count_leaks++;

	if (g_cs_rows[pos].transient_count_leaks == 1)
		g_transient_count_dedup_leaks++;

	g_transient_count_total_leaks++;

	return hook_result;
}

/**
 * Write leak data to all of the various places we need.
 * We force the caller to sprintf() the message first
 * because we want to avoid fprintf() because it allocs.
 */
static void my_output(const char *buf)
{
	fwrite(buf, strlen(buf), 1, stderr);
	OutputDebugString(buf);
}

/**
 * For each row with leaks, dump a stacktrace for it.
 */
static void dump_summary(const char *label)
{
	unsigned int k;
	char buf[10 * 1024];

	if (g_transient_count_total_leaks == 0)
		return;

	fflush(stdout);
	fflush(stderr);
	my_output("\n");

	if (g_limit_reached) {
		sprintf(buf,
				"LEAK SUMMARY: de-dup row table[%d] filled. Increase MY_ROW_LIMIT.\n",
				MY_ROW_LIMIT);
		my_output(buf);
	}

	if (!label)
		label = "";

	if (g_transient_leaks_since_mark) {
		sprintf(buf, "LEAK CHECKPOINT %d: leaks %d unique %d: %s\n",
				g_checkpoint_id, g_transient_count_total_leaks, g_transient_count_dedup_leaks, label);
		my_output(buf);
	} else {
		sprintf(buf, "LEAK SUMMARY: TOTAL leaks %d de-duped %d: %s\n",
				g_transient_count_total_leaks, g_transient_count_dedup_leaks, label);
		my_output(buf);
	}
	my_output("\n");

	for (k = 0; k < g_cs_ins; k++) {
		if (g_cs_rows[k].transient_count_leaks > 0) {
			sprintf(buf, "LEAK: %s leaked %d of %d times:\n",
					g_cs_rows[k].uid.uid,
					g_cs_rows[k].transient_count_leaks,
					g_cs_rows[k].count_allocs);
			my_output(buf);

			if (git_win32__stack_format(
					buf, sizeof(buf), &g_cs_rows[k].raw_data,
					NULL, NULL) >= 0) {
				my_output(buf);
			}

			my_output("\n");
		}
	}

	fflush(stderr);
}

void git_win32__crtdbg_stacktrace_init(void)
{
	InitializeCriticalSection(&g_crtdbg_stacktrace_cs);

	EnterCriticalSection(&g_crtdbg_stacktrace_cs);

	_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);

	_CrtSetReportMode(_CRT_ASSERT, _CRTDBG_MODE_DEBUG | _CRTDBG_MODE_FILE);
	_CrtSetReportMode(_CRT_ERROR,  _CRTDBG_MODE_DEBUG | _CRTDBG_MODE_FILE);
	_CrtSetReportMode(_CRT_WARN,   _CRTDBG_MODE_DEBUG | _CRTDBG_MODE_FILE);

	_CrtSetReportFile(_CRT_ASSERT, _CRTDBG_FILE_STDERR);
	_CrtSetReportFile(_CRT_ERROR,  _CRTDBG_FILE_STDERR);
	_CrtSetReportFile(_CRT_WARN,   _CRTDBG_FILE_STDERR);

	LeaveCriticalSection(&g_crtdbg_stacktrace_cs);
}

int git_win32__crtdbg_stacktrace__dump(
	git_win32__crtdbg_stacktrace_options opt,
	const char *label)
{
	_CRT_REPORT_HOOK old;
	unsigned int k;
	int r = 0;

#define IS_BIT_SET(o,b) (((o) & (b)) != 0)

	bool b_set_mark         = IS_BIT_SET(opt, GIT_WIN32__CRTDBG_STACKTRACE__SET_MARK);
	bool b_leaks_since_mark = IS_BIT_SET(opt, GIT_WIN32__CRTDBG_STACKTRACE__LEAKS_SINCE_MARK);
	bool b_leaks_total      = IS_BIT_SET(opt, GIT_WIN32__CRTDBG_STACKTRACE__LEAKS_TOTAL);
	bool b_quiet            = IS_BIT_SET(opt, GIT_WIN32__CRTDBG_STACKTRACE__QUIET);

	if (b_leaks_since_mark && b_leaks_total) {
		giterr_set(GITERR_INVALID, "Cannot combine LEAKS_SINCE_MARK and LEAKS_TOTAL.");
		return GIT_ERROR;
	}
	if (!b_set_mark && !b_leaks_since_mark && !b_leaks_total) {
		giterr_set(GITERR_INVALID, "Nothing to do.");
		return GIT_ERROR;
	}

	EnterCriticalSection(&g_crtdbg_stacktrace_cs);

	if (b_leaks_since_mark || b_leaks_total) {
		/* All variables with "transient" in the name are per-dump counters
		 * and reset before each dump.  This lets us handle checkpoints.
		 */
		g_transient_count_total_leaks = 0;
		g_transient_count_dedup_leaks = 0;
		for (k = 0; k < g_cs_ins; k++) {
			g_cs_rows[k].transient_count_leaks = 0;
		}
	}

	g_transient_leaks_since_mark = b_leaks_since_mark;

	old = _CrtSetReportHook(report_hook);
	_CrtDumpMemoryLeaks();
	_CrtSetReportHook(old);

	if (b_leaks_since_mark || b_leaks_total) {
		r = g_transient_count_dedup_leaks;

		if (!b_quiet)
			dump_summary(label);
	}

	if (b_set_mark) {
		for (k = 0; k < g_cs_ins; k++) {
			g_cs_rows[k].count_allocs_at_last_checkpoint = g_cs_rows[k].count_allocs;
		}

		g_checkpoint_id++;
	}

	LeaveCriticalSection(&g_crtdbg_stacktrace_cs);

	return r;
}

void git_win32__crtdbg_stacktrace_cleanup(void)
{
	/* At shutdown/cleanup, dump cummulative leak info
	 * with everything since startup.  This might generate
	 * extra noise if the caller has been doing checkpoint
	 * dumps, but it might also eliminate some false
	 * positives for resources previously reported during
	 * checkpoints.
	 */
	git_win32__crtdbg_stacktrace__dump(
		GIT_WIN32__CRTDBG_STACKTRACE__LEAKS_TOTAL,
		"CLEANUP");

	DeleteCriticalSection(&g_crtdbg_stacktrace_cs);
}

const char *git_win32__crtdbg_stacktrace(int skip, const char *file)
{
	git_win32__stack__raw_data new_data;
	git_win32__crtdbg_stacktrace__row *row;
	const char * result = file;

	if (git_win32__stack_capture(&new_data, skip+1) < 0)
		return result;

	EnterCriticalSection(&g_crtdbg_stacktrace_cs);

	if (g_cs_ins < g_cs_end) {
		row = insert_unique(&new_data);
		result = row->uid.uid;
	} else {
		g_limit_reached = true;
	}

	g_count_total_allocs++;

	LeaveCriticalSection(&g_crtdbg_stacktrace_cs);

	return result;
}
#endif