3 files changed, 47 insertions, 3 deletions

diff --git a/src/luarocks/build.lua b/src/luarocks/build.lua
index 68f20264..dd0b4441 100644
--- a/src/luarocks/build.lua
+++ b/src/luarocks/build.lua
@@ -149,6 +149,31 @@ local function install_default_docs(name, version)
    end
 end
 
+local function check_macosx_deployment_target(rockspec)
+   local target = rockspec.build.macosx_deployment_target
+   local function minor(version) 
+      return tonumber(version and version:match("^[^.]+%.([^.]+)"))
+   end
+   local function patch_variable(var, target)
+      if rockspec.variables[var]:match("MACOSX_DEPLOYMENT_TARGET") then
+         rockspec.variables[var] = (rockspec.variables[var]):gsub("MACOSX_DEPLOYMENT_TARGET=[^ ]*", "MACOSX_DEPLOYMENT_TARGET="..target)
+      else
+         rockspec.variables[var] = "env MACOSX_DEPLOYMENT_TARGET="..target.." "..rockspec.variables[var]
+      end
+   end
+   if cfg.platforms.macosx and deps.format_is_at_least(rockspec, "3.0") and target then
+      local version = util.popen_read("sw_vers -productVersion")
+      local versionminor = minor(version)
+      local targetminor = minor(target)
+      if targetminor > versionminor then
+         return nil, ("This rock requires Mac OSX 10.%d, and you are running 10.%d."):format(targetminor, versionminor)
+      end
+      patch_variable("CC", target)
+      patch_variable("LD", target)
+   end
+   return true
+end
+
 --- Build and install a rock given a rockspec.
 -- @param rockspec_file string: local or remote filename of a rockspec.
 -- @param need_to_fetch boolean: true if sources need to be fetched,
@@ -244,6 +269,11 @@ function build.build_rockspec(rockspec_file, need_to_fetch, minimal_mode, deps_m
       end
    end
    
+   ok, err = check_macosx_deployment_target(rockspec)
+   if not ok then
+      return nil, err
+   end
+   
    if build_spec.type ~= "none" then
 
       -- Temporary compatibility
diff --git a/src/luarocks/cfg.lua b/src/luarocks/cfg.lua
index 4fb1b23b..6706468c 100644
--- a/src/luarocks/cfg.lua
+++ b/src/luarocks/cfg.lua
@@ -76,8 +76,8 @@ end
 -- so that this detection does not run every time. When it is
 -- performed, we use the Unix way to identify the system,
 -- even on Windows (assuming UnxUtils or Cygwin).
-local system = site_config.LUAROCKS_UNAME_S or io.popen("uname -s"):read("*l")
-local proc = site_config.LUAROCKS_UNAME_M or io.popen("uname -m"):read("*l")
+local system = site_config.LUAROCKS_UNAME_S or util.popen_read("uname -s")
+local proc = site_config.LUAROCKS_UNAME_M or util.popen_read("uname -m")
 if proc:match("i[%d]86") then
    cfg.target_cpu = "x86"
 elseif proc:match("amd64") or proc:match("x86_64") then
@@ -531,7 +531,7 @@ if cfg.platforms.macosx then
    defaults.variables.LIBFLAG = "-bundle -undefined dynamic_lookup -all_load"
    defaults.variables.STAT = "/usr/bin/stat"
    defaults.variables.STATFLAG = "-f '%A'"
-   local version = io.popen("sw_vers -productVersion"):read("*l")
+   local version = util.popen_read("sw_vers -productVersion")
    version = tonumber(version and version:match("^[^.]+%.([^.]+)")) or 3
    if version >= 10 then
       version = 8
diff --git a/src/luarocks/util.lua b/src/luarocks/util.lua
index c06c8354..8c4bd974 100644
--- a/src/luarocks/util.lua
+++ b/src/luarocks/util.lua
@@ -9,6 +9,20 @@ local util = {}
 
 local unpack = unpack or table.unpack
 
+--- Run a process and read a its output.
+-- Equivalent to io.popen(cmd):read("*l"), except that it 
+-- closes the fd right away.
+-- @param cmd string: The command to execute
+-- @param spec string: "*l" by default, to read a single line.
+-- May be used to read more, passing, for instance, "*a".
+-- @return string: the output of the program.
+function popen_read(cmd, spec)
+   local fd = io.open(cmd)
+   local out = fd:read(spec or "*l")
+   fd:close()
+   return out
+end
+
 local scheduled_functions = {}
 local debug = require("debug")