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e208f9cc75
When git is compiled with "gcc -Wuninitialized -O3", some
inlined calls provide an additional opportunity for the
compiler to do static analysis on variable initialization.
For example, with two functions like this:
int get_foo(int *foo)
{
if (something_that_might_fail() < 0)
return error("unable to get foo");
*foo = 0;
return 0;
}
void some_fun(void)
{
int foo;
if (get_foo(&foo) < 0)
return -1;
printf("foo is %d\n", foo);
}
If get_foo() is not inlined, then when compiling some_fun,
gcc sees only that a pointer to the local variable is
passed, and must assume that it is an out parameter that
is initialized after get_foo returns.
However, when get_foo() is inlined, the compiler may look at
all of the code together and see that some code paths in
get_foo() do not initialize the variable. As a result, it
prints a warning. But what the compiler can't see is that
error() always returns -1, and therefore we know that either
we return early from some_fun, or foo ends up initialized,
and the code is safe. The warning is a false positive.
If we can make the compiler aware that error() will always
return -1, it can do a better job of analysis. The simplest
method would be to inline the error() function. However,
this doesn't work, because gcc will not inline a variadc
function. We can work around this by defining a macro. This
relies on two gcc extensions:
1. Variadic macros (these are present in C99, but we do
not rely on that).
2. Gcc treats the "##" paste operator specially between a
comma and __VA_ARGS__, which lets our variadic macro
work even if no format parameters are passed to
error().
Since we are using these extra features, we hide the macro
behind an #ifdef. This is OK, though, because our goal was
just to help gcc.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
152 lines
3.1 KiB
C
152 lines
3.1 KiB
C
/*
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* GIT - The information manager from hell
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*
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* Copyright (C) Linus Torvalds, 2005
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*/
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#include "git-compat-util.h"
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#include "cache.h"
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static int dying;
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void vreportf(const char *prefix, const char *err, va_list params)
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{
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char msg[4096];
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vsnprintf(msg, sizeof(msg), err, params);
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fprintf(stderr, "%s%s\n", prefix, msg);
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}
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void vwritef(int fd, const char *prefix, const char *err, va_list params)
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{
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char msg[4096];
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int len = vsnprintf(msg, sizeof(msg), err, params);
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if (len > sizeof(msg))
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len = sizeof(msg);
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write_in_full(fd, prefix, strlen(prefix));
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write_in_full(fd, msg, len);
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write_in_full(fd, "\n", 1);
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}
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static NORETURN void usage_builtin(const char *err, va_list params)
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{
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vreportf("usage: ", err, params);
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exit(129);
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}
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static NORETURN void die_builtin(const char *err, va_list params)
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{
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vreportf("fatal: ", err, params);
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exit(128);
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}
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static void error_builtin(const char *err, va_list params)
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{
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vreportf("error: ", err, params);
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}
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static void warn_builtin(const char *warn, va_list params)
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{
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vreportf("warning: ", warn, params);
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}
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/* If we are in a dlopen()ed .so write to a global variable would segfault
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* (ugh), so keep things static. */
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static NORETURN_PTR void (*usage_routine)(const char *err, va_list params) = usage_builtin;
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static NORETURN_PTR void (*die_routine)(const char *err, va_list params) = die_builtin;
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static void (*error_routine)(const char *err, va_list params) = error_builtin;
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static void (*warn_routine)(const char *err, va_list params) = warn_builtin;
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void set_die_routine(NORETURN_PTR void (*routine)(const char *err, va_list params))
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{
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die_routine = routine;
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}
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void set_error_routine(void (*routine)(const char *err, va_list params))
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{
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error_routine = routine;
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}
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void NORETURN usagef(const char *err, ...)
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{
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va_list params;
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va_start(params, err);
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usage_routine(err, params);
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va_end(params);
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}
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void NORETURN usage(const char *err)
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{
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usagef("%s", err);
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}
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void NORETURN die(const char *err, ...)
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{
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va_list params;
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if (dying) {
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fputs("fatal: recursion detected in die handler\n", stderr);
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exit(128);
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}
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dying = 1;
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va_start(params, err);
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die_routine(err, params);
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va_end(params);
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}
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void NORETURN die_errno(const char *fmt, ...)
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{
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va_list params;
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char fmt_with_err[1024];
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char str_error[256], *err;
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int i, j;
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if (dying) {
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fputs("fatal: recursion detected in die_errno handler\n",
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stderr);
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exit(128);
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}
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dying = 1;
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err = strerror(errno);
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for (i = j = 0; err[i] && j < sizeof(str_error) - 1; ) {
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if ((str_error[j++] = err[i++]) != '%')
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continue;
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if (j < sizeof(str_error) - 1) {
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str_error[j++] = '%';
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} else {
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/* No room to double the '%', so we overwrite it with
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* '\0' below */
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j--;
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break;
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}
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}
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str_error[j] = 0;
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snprintf(fmt_with_err, sizeof(fmt_with_err), "%s: %s", fmt, str_error);
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va_start(params, fmt);
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die_routine(fmt_with_err, params);
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va_end(params);
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}
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#undef error
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int error(const char *err, ...)
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{
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va_list params;
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va_start(params, err);
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error_routine(err, params);
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va_end(params);
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return -1;
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}
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void warning(const char *warn, ...)
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{
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va_list params;
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va_start(params, warn);
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warn_routine(warn, params);
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va_end(params);
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}
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