On 06/28/2015 04:05 PM, Paul Tan wrote:
A common usage pattern of open() is to check if it was successful, and
die() if it was not:
int fd = open(path, O_WRONLY | O_CREAT, 0777);
if (fd < 0)
die_errno(_("Could not open '%s' for writing."), path);
Implement a wrapper function xopen() that does the above so that we can
save a few lines of code, and make the die() messages consistent.
Helped-by: Torsten Bögershausen <tboegi@xxxxxx>
Helped-by: Jeff King <peff@xxxxxxxx>
Signed-off-by: Paul Tan <pyokagan@xxxxxxxxx>
---
git-compat-util.h | 1 +
wrapper.c | 25 +++++++++++++++++++++++++
2 files changed, 26 insertions(+)
diff --git a/git-compat-util.h b/git-compat-util.h
index c6d391f..e168dfd 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -717,6 +717,7 @@ extern void *xrealloc(void *ptr, size_t size);
extern void *xcalloc(size_t nmemb, size_t size);
extern void *xmmap(void *start, size_t length, int prot, int flags, int fd, off_t offset);
extern void *xmmap_gently(void *start, size_t length, int prot, int flags, int fd, off_t offset);
+extern int xopen(const char *path, int flags, ...);
extern ssize_t xread(int fd, void *buf, size_t len);
extern ssize_t xwrite(int fd, const void *buf, size_t len);
extern ssize_t xpread(int fd, void *buf, size_t len, off_t offset);
diff --git a/wrapper.c b/wrapper.c
index ff49807..7e13ae0 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -189,6 +189,31 @@ void *xcalloc(size_t nmemb, size_t size)
# endif
#endif
+/**
+ * xopen() is the same as open(), but it die()s if the open() fails.
+ */
+int xopen(const char *path, int oflag, ...)
+{
+ mode_t mode = 0;
+ va_list ap;
+
+ va_start(ap, oflag);
+ if (oflag & O_CREAT)
+ mode = va_arg(ap, mode_t);
+ va_end(ap);
+
+ assert(path);
+
2 remarks:
- I don't know if and why we need the assert() here (but don't know if
we have a strategie in Git for assert())
- Having xopen() with 2 or 3 parameter is good, but the current may need
some tweaks for better portability:
int xopen(const char *path, int oflag, ...)
{
mode_t mode = 0;
if (oflag & O_CREAT) {
va_list ap;
va_start(ap, oflag);
mode = va_arg(ap, int);
va_end(ap);
}
See e.g.
<http://blitiri.com.ar/git/r/libfiu/c/37f6a98110e3bb59bbb4971241baa3a385c3f724/>
why va_arg(ap, int) should be used:
+
+ /* va_arg() can only take fully promoted types, and mode_t
+ * sometimes is smaller than an int, so we should always pass
+ * int to it, and not mode_t. Not doing so would may result in
+ * a compile-time warning and run-time error. We asume that it
+ * is never bigger than an int, which holds in practise. */
+ mode = va_arg(l, int);
+
--
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