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 <p...@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
--
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