[PATCH v2] vcs-svn: Fix some compiler warnings

From: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Date: Feb 2, 2012, 18:36 UTC
Message-ID: <4F2AD7AA.9090904@ramsay1.demon.co.uk>

In particular, some versions of gcc complains as follows:

        CC vcs-svn/sliding_window.o
    vcs-svn/sliding_window.c: In function `check_overflow':
    vcs-svn/sliding_window.c:36: warning: comparison is always false \
        due to limited range of data type

        CC vcs-svn/fast_export.o
    vcs-svn/fast_export.c: In function `fast_export_blob_delta':
    vcs-svn/fast_export.c:303: warning: comparison is always false due \
        to limited range of data type

Simply casting the (limited range unsigned) variable in the comparison to an uintmax_t does not suppress the warning, however, since gcc is "smart" enough to know that the cast does not change anything regarding the value of the casted expression. In order to suppress the warning, we introduce a static inline function to hide the (implicit) cast of the original variable to an uintmax_t type prior to using it in the overflow check comparison expression.

Note that the "some versions of gcc" which complain includes 3.4.4 and 4.1.2, whereas gcc version 4.4.0 compiles the code without complaint.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
---

Hi Jonathan,

Any suggestions for a better name than "value_too_large_for_off_t" will be greatly accepted! :)

Also, I suppose you could make a similar change to the other two sites in vcs-svn with similar range checks (fast_export.c:174 and svndiff.c:150).

ATB, Ramsay Jones

 git-compat-util.h        |    5 +++++
 vcs-svn/fast_export.c    |    2 +-
 vcs-svn/sliding_window.c |    2 +-
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/git-compat-util.h b/git-compat-util.h
index 8f3972c..6a6a25a 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -450,6 +450,11 @@ static inline size_t xsize_t(off_t len)
 	return (size_t)len;
 }
 
+static inline int value_too_large_for_off_t(uintmax_t val)
+{
+	return val > maximum_signed_value_of_type(off_t);
+}
+
 static inline int has_extension(const char *filename, const char *ext)
 {
 	size_t len = strlen(filename);
diff --git a/vcs-svn/fast_export.c b/vcs-svn/fast_export.c
index 19d7c34..2e0dcb0 100644
--- a/vcs-svn/fast_export.c
+++ b/vcs-svn/fast_export.c
@@ -300,7 +300,7 @@ void fast_export_blob_delta(uint32_t mode,
 				uint32_t len, struct line_buffer *input)
 {
 	long postimage_len;
-	if (len > maximum_signed_value_of_type(off_t))
+	if (value_too_large_for_off_t(len))
 		die("enormous delta");
 	postimage_len = apply_delta((off_t) len, input, old_data, old_mode);
 	if (mode == REPO_MODE_LNK) {
diff --git a/vcs-svn/sliding_window.c b/vcs-svn/sliding_window.c
index 1bac7a4..0d38482 100644
--- a/vcs-svn/sliding_window.c
+++ b/vcs-svn/sliding_window.c
@@ -33,7 +33,7 @@ static int read_to_fill_or_whine(struct line_buffer *file,
 
 static int check_overflow(off_t a, size_t b)
 {
-	if (b > maximum_signed_value_of_type(off_t))
+	if (value_too_large_for_off_t(b))
 		return error("unrepresentable length in delta: "
 				"%"PRIuMAX" > OFF_MAX", (uintmax_t) b);
 	if (signed_add_overflows(a, (off_t) b))

-- 
1.7.9