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git/usage.c
Johannes Schindelin 116d1fa6c6 vreportf(): avoid relying on stdio buffering
The MSVC runtime behavior differs from glibc's with respect to
`fprintf(stderr, ...)` in that the former writes out the message
character by character.

In t5516, this leads to a funny problem where a `git fetch` process as
well as the `git upload-pack` process spawned by it _both_ call `die()`
at the same time. The output can look like this:

	fatal: git uploadfata-lp: raemcokte :error:  upload-pnot our arcef k6: n4ot our ea4cr1e3f 36d45ea94fca1398e86a771eda009872d63adb28598f6a9
	8e86a771eda009872d6ab2886

Let's avoid this predicament altogether by rendering the entire message,
including the prefix and the trailing newline, into the buffer we
already have (and which is still fixed size) and then write it out via
`write_in_full()`.

We still clip the message to at most 4095 characters.

The history of `vreportf()` with regard to this issue includes the
following commits:

d048a96e (2007-11-09) - 'char msg[256]' is introduced to avoid interleaving
389d1767 (2009-03-25) - Buffer size increased to 1024 to avoid truncation
625a860c (2009-11-22) - Buffer size increased to 4096 to avoid truncation
f4c3edc0 (2015-08-11) - Buffer removed to avoid truncation
b5a9e435 (2017-01-11) - Reverts f4c3edc0 to be able to replace control
                        chars before sending to stderr
9ac13ec9 (2006-10-11) - Another attempt to solve interleaving.
                        This is seemingly related to d048a96e.
137a0d0e (2007-11-19) - Addresses out-of-order for display()
34df8aba (2009-03-10) - Switches xwrite() to fprintf() in recv_sideband()
                        to support UTF-8 emulation
eac14f89 (2012-01-14) - Removes the need for fprintf() for UTF-8 emulation,
                        so it's safe to use xwrite() again
5e5be9e2 (2016-06-28) - recv_sideband() uses xwrite() again

Note that we print nothing if the `vsnprintf()` call failed to render
the error message; There is little we can do in that case, and it should
not happen anyway.

The process may have written to `stderr` and there may be something left
in the buffer kept in the stdio layer. Call `fflush(stderr)` before
writing the message we prepare in this function.

Helped-by: Jeff King <peff@peff.net>
Helped-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
Helped-by: SZEDER Gábor <szeder.dev@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-11-02 15:20:21 +09:00

307 lines
6.7 KiB
C

/*
* GIT - The information manager from hell
*
* Copyright (C) Linus Torvalds, 2005
*/
#include "git-compat-util.h"
#include "cache.h"
void vreportf(const char *prefix, const char *err, va_list params)
{
char msg[4096];
char *p, *pend = msg + sizeof(msg);
size_t prefix_len = strlen(prefix);
if (sizeof(msg) <= prefix_len) {
fprintf(stderr, "BUG!!! too long a prefix '%s'\n", prefix);
abort();
}
memcpy(msg, prefix, prefix_len);
p = msg + prefix_len;
if (vsnprintf(p, pend - p, err, params) < 0)
*p = '\0'; /* vsnprintf() failed, clip at prefix */
for (; p != pend - 1 && *p; p++) {
if (iscntrl(*p) && *p != '\t' && *p != '\n')
*p = '?';
}
*(p++) = '\n'; /* we no longer need a NUL */
fflush(stderr);
write_in_full(2, msg, p - msg);
}
static NORETURN void usage_builtin(const char *err, va_list params)
{
vreportf("usage: ", err, params);
/*
* When we detect a usage error *before* the command dispatch in
* cmd_main(), we don't know what verb to report. Force it to this
* to facilitate post-processing.
*/
trace2_cmd_name("_usage_");
/*
* Currently, the (err, params) are usually just the static usage
* string which isn't very useful here. Usually, the call site
* manually calls fprintf(stderr,...) with the actual detailed
* syntax error before calling usage().
*
* TODO It would be nice to update the call sites to pass both
* the static usage string and the detailed error message.
*/
exit(129);
}
static NORETURN void die_builtin(const char *err, va_list params)
{
/*
* We call this trace2 function first and expect it to va_copy 'params'
* before using it (because an 'ap' can only be walked once).
*/
trace2_cmd_error_va(err, params);
vreportf("fatal: ", err, params);
exit(128);
}
static void error_builtin(const char *err, va_list params)
{
/*
* We call this trace2 function first and expect it to va_copy 'params'
* before using it (because an 'ap' can only be walked once).
*/
trace2_cmd_error_va(err, params);
vreportf("error: ", err, params);
}
static void warn_builtin(const char *warn, va_list params)
{
vreportf("warning: ", warn, params);
}
static int die_is_recursing_builtin(void)
{
static int dying;
/*
* Just an arbitrary number X where "a < x < b" where "a" is
* "maximum number of pthreads we'll ever plausibly spawn" and
* "b" is "something less than Inf", since the point is to
* prevent infinite recursion.
*/
static const int recursion_limit = 1024;
dying++;
if (dying > recursion_limit) {
return 1;
} else if (dying == 2) {
warning("die() called many times. Recursion error or racy threaded death!");
return 0;
} else {
return 0;
}
}
/* If we are in a dlopen()ed .so write to a global variable would segfault
* (ugh), so keep things static. */
static NORETURN_PTR void (*usage_routine)(const char *err, va_list params) = usage_builtin;
static NORETURN_PTR void (*die_routine)(const char *err, va_list params) = die_builtin;
static void (*error_routine)(const char *err, va_list params) = error_builtin;
static void (*warn_routine)(const char *err, va_list params) = warn_builtin;
static int (*die_is_recursing)(void) = die_is_recursing_builtin;
void set_die_routine(NORETURN_PTR void (*routine)(const char *err, va_list params))
{
die_routine = routine;
}
void set_error_routine(void (*routine)(const char *err, va_list params))
{
error_routine = routine;
}
void (*get_error_routine(void))(const char *err, va_list params)
{
return error_routine;
}
void set_warn_routine(void (*routine)(const char *warn, va_list params))
{
warn_routine = routine;
}
void (*get_warn_routine(void))(const char *warn, va_list params)
{
return warn_routine;
}
void set_die_is_recursing_routine(int (*routine)(void))
{
die_is_recursing = routine;
}
void NORETURN usagef(const char *err, ...)
{
va_list params;
va_start(params, err);
usage_routine(err, params);
va_end(params);
}
void NORETURN usage(const char *err)
{
usagef("%s", err);
}
void NORETURN die(const char *err, ...)
{
va_list params;
if (die_is_recursing()) {
fputs("fatal: recursion detected in die handler\n", stderr);
exit(128);
}
va_start(params, err);
die_routine(err, params);
va_end(params);
}
static const char *fmt_with_err(char *buf, int n, const char *fmt)
{
char str_error[256], *err;
int i, j;
err = strerror(errno);
for (i = j = 0; err[i] && j < sizeof(str_error) - 1; ) {
if ((str_error[j++] = err[i++]) != '%')
continue;
if (j < sizeof(str_error) - 1) {
str_error[j++] = '%';
} else {
/* No room to double the '%', so we overwrite it with
* '\0' below */
j--;
break;
}
}
str_error[j] = 0;
/* Truncation is acceptable here */
snprintf(buf, n, "%s: %s", fmt, str_error);
return buf;
}
void NORETURN die_errno(const char *fmt, ...)
{
char buf[1024];
va_list params;
if (die_is_recursing()) {
fputs("fatal: recursion detected in die_errno handler\n",
stderr);
exit(128);
}
va_start(params, fmt);
die_routine(fmt_with_err(buf, sizeof(buf), fmt), params);
va_end(params);
}
#undef error_errno
int error_errno(const char *fmt, ...)
{
char buf[1024];
va_list params;
va_start(params, fmt);
error_routine(fmt_with_err(buf, sizeof(buf), fmt), params);
va_end(params);
return -1;
}
#undef error
int error(const char *err, ...)
{
va_list params;
va_start(params, err);
error_routine(err, params);
va_end(params);
return -1;
}
void warning_errno(const char *warn, ...)
{
char buf[1024];
va_list params;
va_start(params, warn);
warn_routine(fmt_with_err(buf, sizeof(buf), warn), params);
va_end(params);
}
void warning(const char *warn, ...)
{
va_list params;
va_start(params, warn);
warn_routine(warn, params);
va_end(params);
}
/* Only set this, ever, from t/helper/, when verifying that bugs are caught. */
int BUG_exit_code;
static NORETURN void BUG_vfl(const char *file, int line, const char *fmt, va_list params)
{
char prefix[256];
/* truncation via snprintf is OK here */
if (file)
snprintf(prefix, sizeof(prefix), "BUG: %s:%d: ", file, line);
else
snprintf(prefix, sizeof(prefix), "BUG: ");
vreportf(prefix, fmt, params);
if (BUG_exit_code)
exit(BUG_exit_code);
abort();
}
#ifdef HAVE_VARIADIC_MACROS
NORETURN void BUG_fl(const char *file, int line, const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
BUG_vfl(file, line, fmt, ap);
va_end(ap);
}
#else
NORETURN void BUG(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
BUG_vfl(NULL, 0, fmt, ap);
va_end(ap);
}
#endif
#ifdef SUPPRESS_ANNOTATED_LEAKS
void unleak_memory(const void *ptr, size_t len)
{
static struct suppressed_leak_root {
struct suppressed_leak_root *next;
char data[FLEX_ARRAY];
} *suppressed_leaks;
struct suppressed_leak_root *root;
FLEX_ALLOC_MEM(root, data, ptr, len);
root->next = suppressed_leaks;
suppressed_leaks = root;
}
#endif