[PATCH/RFC 3/3] silence some -Wuninitialized warnings around errors
- From
Jeff King <peff@peff.net>
- Date
- Dec 14, 2012, 22:13 UTC
- Message-ID
- <20121214221317.GC19677@sigill.intra.peff.net>
- In-Reply-To
- <20121214220903.GA18418@sigill.intra.peff.net>
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.
By converting the error() call to:
error("unable to get foo");
return -1;we explicitly make the compiler aware of the constant return value, and it silences the warning.
Signed-off-by: Jeff King <peff@peff.net> --- Not sure if we should do this or not. This does silence the warnings, but it's kind of ugly.
builtin/reflog.c | 6 ++++-- vcs-svn/svndiff.c | 6 ++++-- 2 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/builtin/reflog.c b/builtin/reflog.c index b3c9e27..c2ea9d3 100644 --- a/builtin/reflog.c +++ b/builtin/reflog.c @@ -494,8 +494,10 @@ static int parse_expire_cfg_value(const char *var, const char *value, unsigned l static int parse_expire_cfg_value(const char *var, const char *value, unsigned long *expire) { - if (!value) - return config_error_nonbool(var); + if (!value) { + config_error_nonbool(var); + return -1; + } if (!strcmp(value, "never") || !strcmp(value, "false")) { *expire = 0; return 0; diff --git a/vcs-svn/svndiff.c b/vcs-svn/svndiff.c index 74c97c4..46e96f6 100644 --- a/vcs-svn/svndiff.c +++ b/vcs-svn/svndiff.c @@ -121,7 +121,8 @@ static int read_int(struct line_buffer *in, uintmax_t *result, off_t *len) *len = sz - 1; return 0; } - return error_short_read(in); + error_short_read(in); + return -1; } static int parse_int(const char **buf, size_t *result, const char *end) @@ -140,7 +141,8 @@ static int parse_int(const char **buf, size_t *result, const char *end) *buf = pos + 1; return 0; } - return error("invalid delta: unexpected end of instructions section"); + error("invalid delta: unexpected end of instructions section"); + return -1; } static int read_offset(struct line_buffer *in, off_t *result, off_t *len)
-- 1.8.0.2.4.g59402aa