temporary: nix: Work around for broken stat size #1645

temporary/all-temporary.nix

@@ -7,4 +7,9 @@
 
 self: super: pkgs: with pkgs; {
 
+  # https://github.com/NixOS/nix/pull/1645
+  nixStable = super.nixStable.overrideAttrs
+    ( attrs: { patches = attrs.patches or [] ++ [ ./nix/stat.patch ]; } );
+  nix = super.nix.overrideAttrs
+    ( attrs: { patches = attrs.patches or [] ++ [ ./nix/stat.patch ]; } );
 }

temporary/nix/stat.patch

@@ -0,0 +1,33 @@
+diff --git a/src/libutil/util.cc b/src/libutil/util.cc
+index 0b11330..4c1dff2 100644
+--- a/src/libutil/util.cc
++++ b/src/libutil/util.cc
+@@ -198,17 +198,17 @@ bool pathExists(const Path & path)
+ Path readLink(const Path & path)
+ {
+     checkInterrupt();
+-    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);
+-    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);
++    for (ssize_t bufSize = PATH_MAX/4; true; bufSize += bufSize/2) {
++        char buf[bufSize];
++        ssize_t rlSize = readlink(path.c_str(), buf, bufSize);
++        if (rlSize == -1)
++            if (errno == EINVAL)
++                throw Error(format("'%1%' is not a symlink") % path);
++            else
++                throw SysError(format("reading symbolic link '%1%'") % path);
++        else if (rlSize < bufSize)
++            return string(buf, rlSize);
++    }
+ }
+ 
+