lib: deprecate memset_zero template, use C99 compound literals instead

Sprinkle in some asserts to make sure compilers aren't getting creative.

This may introduce a new compiler dependency, as I suspect older versions
of GCC don't support this syntax.

It definitely needs a new compiler flag to suppress a warning when some
fields are not explicitly initialized.  If we've omitted a field, it's
because it's a field we don't know (or care) about, and we want that
thing initialized to zero.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

include/crucible/string.h

@@ -11,14 +11,6 @@
 namespace crucible {
 	using namespace std;
 
-	// Zero-initialize a base class object (usually a C struct)
-	template <class Base>
-	void
-	memset_zero(Base *that)
-	{
-		memset(that, 0, sizeof(Base));
-	}
-
 	// int->hex conversion with sprintf
 	string to_hex(uint64_t i);
 

lib/fd.cc

@@ -477,9 +477,9 @@ namespace crucible {
 		return pwrite_or_die(fd, text.data(), text.size(), offset);
 	}
 
-	Stat::Stat()
+	Stat::Stat() :
+		stat( (stat) { } )
 	{
-		memset_zero<stat>(this);
 	}
 
 	Stat &
@@ -498,15 +498,15 @@ namespace crucible {
 		return *this;
 	}
 
-	Stat::Stat(int fd)
+	Stat::Stat(int fd) :
+		stat( (stat) { } )
 	{
-		memset_zero<stat>(this);
 		fstat(fd);
 	}
 
-	Stat::Stat(const string &filename)
+	Stat::Stat(const string &filename) :
+		stat( (stat) { } )
 	{
-		memset_zero<stat>(this);
 		lstat(filename);
 	}
 

lib/fs.cc

@@ -32,17 +32,24 @@ namespace crucible {
 #endif
 	}
 
-	BtrfsExtentInfo::BtrfsExtentInfo(int dst_fd, off_t dst_offset)
+	BtrfsExtentInfo::BtrfsExtentInfo(int dst_fd, off_t dst_offset) :
+		btrfs_ioctl_same_extent_info( (btrfs_ioctl_same_extent_info) { } )
 	{
-		memset_zero<btrfs_ioctl_same_extent_info>(this);
+		assert(fd == 0);
+		assert(logical_offset == 0);
+		assert(bytes_deduped == 0);
+		assert(status == 0);
+		assert(reserved == 0);
 		fd = dst_fd;
 		logical_offset = dst_offset;
 	}
 
 	BtrfsExtentSame::BtrfsExtentSame(int src_fd, off_t src_offset, off_t src_length) :
+		btrfs_ioctl_same_args( (btrfs_ioctl_same_args) { } ),
 		m_fd(src_fd)
 	{
-		memset_zero<btrfs_ioctl_same_args>(this);
+		assert(logical_offset == 0);
+		assert(length == 0);
 		logical_offset = src_offset;
 		length = src_length;
 	}
@@ -126,12 +133,12 @@ namespace crucible {
 	void
 	btrfs_clone_range(int src_fd, off_t src_offset, off_t src_length, int dst_fd, off_t dst_offset)
 	{
-		struct btrfs_ioctl_clone_range_args args;
+		btrfs_ioctl_clone_range_args args ( (btrfs_ioctl_clone_range_args) {
-		memset_zero(&args);
+			.src_fd = src_fd,
-		args.src_fd = src_fd;
+			.src_offset = ranged_cast<uint64_t, off_t>(src_offset),
-		args.src_offset = src_offset;
+			.src_length = ranged_cast<uint64_t, off_t>(src_length),
-		args.src_length = src_length;
+			.dest_offset = ranged_cast<uint64_t, off_t>(dst_offset),
-		args.dest_offset = dst_offset;
+		} );
 		DIE_IF_MINUS_ONE(ioctl(dst_fd, BTRFS_IOC_CLONE_RANGE, &args));
 	}
 
@@ -257,10 +264,13 @@ namespace crucible {
 	}
 
 	BtrfsIoctlLogicalInoArgs::BtrfsIoctlLogicalInoArgs(uint64_t new_logical, size_t new_size) :
+		btrfs_ioctl_logical_ino_args( (btrfs_ioctl_logical_ino_args) { } ),
 		m_container_size(new_size),
 		m_container(new_size)
 	{
-		memset_zero<btrfs_ioctl_logical_ino_args>(this);
+		assert(logical == 0);
+		assert(size == 0);
+		assert(flags == 0);
 		logical = new_logical;
 	}
 
@@ -396,9 +406,10 @@ namespace crucible {
 	}
 
 	BtrfsIoctlInoPathArgs::BtrfsIoctlInoPathArgs(uint64_t inode, size_t new_size) :
+		btrfs_ioctl_ino_path_args( (btrfs_ioctl_ino_path_args) { } ),
 		m_container_size(new_size)
 	{
-		memset_zero<btrfs_ioctl_ino_path_args>(this);
+		assert(inum == 0);
 		inum = inode;
 	}
 
@@ -458,9 +469,10 @@ namespace crucible {
 		return os;
 	}
 
-	BtrfsIoctlInoLookupArgs::BtrfsIoctlInoLookupArgs(uint64_t new_objectid)
+	BtrfsIoctlInoLookupArgs::BtrfsIoctlInoLookupArgs(uint64_t new_objectid) :
+		btrfs_ioctl_ino_lookup_args( (btrfs_ioctl_ino_lookup_args) { } )
 	{
-		memset_zero<btrfs_ioctl_ino_lookup_args>(this);
+		assert(objectid == 0);
 		objectid = new_objectid;
 	}
 
@@ -478,9 +490,9 @@ namespace crucible {
 		}
 	}
 
-	BtrfsIoctlDefragRangeArgs::BtrfsIoctlDefragRangeArgs()
+	BtrfsIoctlDefragRangeArgs::BtrfsIoctlDefragRangeArgs() :
+		btrfs_ioctl_defrag_range_args( (btrfs_ioctl_defrag_range_args) { } )
 	{
-		memset_zero<btrfs_ioctl_defrag_range_args>(this);
 	}
 
 	bool
@@ -537,9 +549,9 @@ namespace crucible {
 		return os;
 	}
 
-	FiemapExtent::FiemapExtent()
+	FiemapExtent::FiemapExtent() :
+		fiemap_extent( (fiemap_extent) { } )
 	{
-		memset_zero<fiemap_extent>(this);
 	}
 
 	FiemapExtent::FiemapExtent(const fiemap_extent &that)
@@ -660,14 +672,15 @@ namespace crucible {
 		return os << "\n}";
 	}
 
-	Fiemap::Fiemap(uint64_t start, uint64_t length)
+	Fiemap::Fiemap(uint64_t start, uint64_t length) :
-	{
+		fiemap( (fiemap) {
-		memset_zero<fiemap>(this);
+			.fm_start = start,
-		fm_start = start;
+			.fm_length = length,
-		fm_length = length;
+			// FIEMAP is slow and full of lies.
-		// FIEMAP is slow and full of lines.
 			// This makes FIEMAP even slower, but reduces the lies a little.
-		fm_flags = FIEMAP_FLAG_SYNC;
+			.fm_flags = FIEMAP_FLAG_SYNC,
+		})
+	{
 	}
 
 	void
@@ -727,19 +740,20 @@ namespace crucible {
 	}
 
 	BtrfsIoctlSearchKey::BtrfsIoctlSearchKey(size_t buf_size) :
+		btrfs_ioctl_search_key( (btrfs_ioctl_search_key) {
+			.max_objectid = numeric_limits<decltype(max_objectid)>::max(),
+			.max_offset = numeric_limits<decltype(max_offset)>::max(),
+			.max_transid = numeric_limits<decltype(max_transid)>::max(),
+			.max_type = numeric_limits<decltype(max_type)>::max(),
+			.nr_items = 1,
+		}),
 		m_buf_size(buf_size)
 	{
-		memset_zero<btrfs_ioctl_search_key>(this);
-		max_objectid = numeric_limits<decltype(max_objectid)>::max();
-		max_offset = numeric_limits<decltype(max_offset)>::max();
-		max_transid = numeric_limits<decltype(max_transid)>::max();
-		max_type = numeric_limits<decltype(max_type)>::max();
-		nr_items = 1;
 	}
 
-	BtrfsIoctlSearchHeader::BtrfsIoctlSearchHeader()
+	BtrfsIoctlSearchHeader::BtrfsIoctlSearchHeader() :
+		btrfs_ioctl_search_header( (btrfs_ioctl_search_header) { } )
 	{
-		memset_zero<btrfs_ioctl_search_header>(this);
 	}
 
 	size_t
@@ -1084,9 +1098,9 @@ namespace crucible {
 		return rv;
 	}
 
-	Statvfs::Statvfs()
+	Statvfs::Statvfs() :
+		statvfs( (statvfs) { } )
 	{
-		memset_zero<statvfs>(this);
 	}
 
 	Statvfs::Statvfs(int fd) :
@@ -1137,10 +1151,11 @@ namespace crucible {
 		return os << " }";
 	};
 
-	BtrfsIoctlFsInfoArgs::BtrfsIoctlFsInfoArgs()
+	BtrfsIoctlFsInfoArgs::BtrfsIoctlFsInfoArgs() :
+		btrfs_ioctl_fs_info_args_v2( (btrfs_ioctl_fs_info_args_v2) {
+			.flags = BTRFS_FS_INFO_FLAG_CSUM_INFO,
+		})
 	{
-		memset_zero<btrfs_ioctl_fs_info_args_v2>(this);
-		flags = BTRFS_FS_INFO_FLAG_CSUM_INFO;
 	}
 
 	void

makeflags

@@ -10,4 +10,4 @@ CCFLAGS = -Wall -Wextra -Werror -O3
 CCFLAGS += -I../include -D_FILE_OFFSET_BITS=64
 
 BEES_CFLAGS   = $(CCFLAGS) -std=c99 $(CFLAGS)
-BEES_CXXFLAGS = $(CCFLAGS) -std=c++11 -Wold-style-cast $(CXXFLAGS)
+BEES_CXXFLAGS = $(CCFLAGS) -std=c++11 -Wold-style-cast -Wno-missing-field-initializers $(CXXFLAGS)