daemon: Use std::string or std::vector instead of variable-length array (VLA).

* libutil/util.h (waitForMessage): Use std::string instead of char* to unify coding style.
* libutil/util.cc (waitForMessage): Use std::string instead of variable-length array (VLA).
(readLink, copyFileRecursively, expect): Use std::vector instead of VLA.
* libutil/hash.cc (printHash): Use std::vector instead of VLA.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

3 files changed, 16 insertions, 17 deletions

diff --git a/nix/libutil/hash.cc b/nix/libutil/hash.cc
index 9b83ffcdd9b..3cb4d05318b 100644
--- a/nix/libutil/hash.cc
+++ b/nix/libutil/hash.cc
@@ -64,12 +64,12 @@ const string base16Chars = "0123456789abcdef";
 
 string printHash(const Hash & hash)
 {
-    char buf[hash.hashSize * 2];
+    std::vector<char> buf(hash.hashSize * 2);
     for (unsigned int i = 0; i < hash.hashSize; i++) {
         buf[i * 2] = base16Chars[hash.hash[i] >> 4];
         buf[i * 2 + 1] = base16Chars[hash.hash[i] & 0x0f];
     }
-    return string(buf, hash.hashSize * 2);
+    return string(buf.begin(), buf.end());
 }
 
 
diff --git a/nix/libutil/util.cc b/nix/libutil/util.cc
index 8938a213f6d..9a97270af90 100644
--- a/nix/libutil/util.cc
+++ b/nix/libutil/util.cc
@@ -223,14 +223,14 @@ Path readLink(const Path & path)
     struct stat st = lstat(path);
     if (!S_ISLNK(st.st_mode))
         throw Error(format("`%1%' is not a symlink") % path);
-    char buf[st.st_size];
-    ssize_t rlsize = readlink(path.c_str(), buf, st.st_size);
+    std::vector<char> buf(st.st_size);
+    ssize_t rlsize = readlink(path.c_str(), buf.data(), st.st_size);
     if (rlsize == -1)
         throw SysError(format("reading symbolic link '%1%'") % path);
     else if (rlsize > st.st_size)
         throw Error(format("symbolic link ‘%1%’ size overflow %2% > %3%")
             % path % rlsize % st.st_size);
-    return string(buf, st.st_size);
+    return string(buf.begin(), buf.end());
 }
 
 
@@ -481,11 +481,11 @@ static void copyFileRecursively(int sourceroot, const Path &source,
         copyFile(sourceFd, destinationFd);
         fchown(destinationFd, st.st_uid, st.st_gid);
     } else if (S_ISLNK(st.st_mode)) {
-        char target[st.st_size + 1];
-        ssize_t result = readlinkat(sourceroot, source.c_str(), target, st.st_size);
+    std::vector<char> target(st.st_size + 1);
+        ssize_t result = readlinkat(sourceroot, source.c_str(), target.data(), st.st_size);
         if (result != st.st_size) throw SysError("reading symlink target");
         target[st.st_size] = '\0';
-        int err = symlinkat(target, destinationroot, destination.c_str());
+        int err = symlinkat(target.data(), destinationroot, destination.c_str());
         if (err != 0)
             throw SysError(format("creating symlink `%1%'") % destination);
         fchownat(destinationroot, destination.c_str(),
@@ -749,12 +749,11 @@ string drainFD(int fd)
 
 
 /* Wait on FD until MESSAGE has been read.  */
-void waitForMessage(int fd, const char *message)
+void waitForMessage(int fd, const string & message)
 {
-    size_t size = strlen(message);
-    char str[size] = { '\0' };
-    readFull(fd, (unsigned char*)str, size);
-    if (strncmp(str, message, size) != 0)
+    string str(message.length(), '\0');
+    readFull(fd, (unsigned char*)str.data(), message.length());
+    if (str != message)
         throw Error(format("did not receive message '%1%' on file descriptor %2%")
             % message % fd);
 }
@@ -1348,9 +1347,9 @@ bool hasSuffix(const string & s, const string & suffix)
 
 void expect(std::istream & str, const string & s)
 {
-    char s2[s.size()];
-    str.read(s2, s.size());
-    if (string(s2, s.size()) != s)
+    std::vector<char> s2(s.size());
+    str.read(s2.data(), s2.size());
+    if (string(s2.begin(), s2.end()) != s)
         throw FormatError(format("expected string `%1%'") % s);
 }
 
diff --git a/nix/libutil/util.hh b/nix/libutil/util.hh
index 648d6f19a4c..7b50dfa5f58 100644
--- a/nix/libutil/util.hh
+++ b/nix/libutil/util.hh
@@ -179,7 +179,7 @@ MakeError(EndOfFile, Error)
 /* Read a file descriptor until EOF occurs. */
 string drainFD(int fd);
 
-void waitForMessage(int fd, const char *message);
+void waitForMessage(int fd, const string & message);