Fix calls to retry_with_buffer when big buffer is necessary (#14622)

Co-authored-by: Johannes Müller <[email protected]>

Author: BlobCodes

src/crystal/system/unix/group.cr

@@ -12,9 +12,9 @@ module Crystal::System::Group
     groupname.check_no_null_byte
 
     grp = uninitialized LibC::Group
-    grp_pointer = pointerof(grp)
+    grp_pointer = Pointer(LibC::Group).null
     System.retry_with_buffer("getgrnam_r", GETGR_R_SIZE_MAX) do |buf|
-      LibC.getgrnam_r(groupname, grp_pointer, buf, buf.size, pointerof(grp_pointer)).tap do
+      LibC.getgrnam_r(groupname, pointerof(grp), buf, buf.size, pointerof(grp_pointer)).tap do
         # It's not necessary to check success with `ret == 0` because `grp_pointer` will be NULL on failure
         return from_struct(grp) if grp_pointer
       end
@@ -26,9 +26,9 @@ module Crystal::System::Group
     return unless groupid
 
     grp = uninitialized LibC::Group
-    grp_pointer = pointerof(grp)
+    grp_pointer = Pointer(LibC::Group).null
     System.retry_with_buffer("getgrgid_r", GETGR_R_SIZE_MAX) do |buf|
-      LibC.getgrgid_r(groupid, grp_pointer, buf, buf.size, pointerof(grp_pointer)).tap do
+      LibC.getgrgid_r(groupid, pointerof(grp), buf, buf.size, pointerof(grp_pointer)).tap do
         # It's not necessary to check success with `ret == 0` because `grp_pointer` will be NULL on failure
         return from_struct(grp) if grp_pointer
       end

src/crystal/system/unix/path.cr

@@ -8,16 +8,16 @@ module Crystal::System::Path
       id = LibC.getuid
 
       pwd = uninitialized LibC::Passwd
-      pwd_pointer = pointerof(pwd)
-      ret = nil
+      pwd_pointer = Pointer(LibC::Passwd).null
+      ret = LibC::Int.new(0)
       System.retry_with_buffer("getpwuid_r", User::GETPW_R_SIZE_MAX) do |buf|
-        ret = LibC.getpwuid_r(id, pwd_pointer, buf, buf.size, pointerof(pwd_pointer)).tap do
+        ret = LibC.getpwuid_r(id, pointerof(pwd), buf, buf.size, pointerof(pwd_pointer)).tap do
           # It's not necessary to check success with `ret == 0` because `pwd_pointer` will be NULL on failure
           return String.new(pwd.pw_dir) if pwd_pointer
         end
       end
 
-      raise RuntimeError.from_os_error("getpwuid_r", Errno.new(ret.not_nil!))
+      raise RuntimeError.from_os_error("getpwuid_r", Errno.new(ret))
     end
   end
 end

src/crystal/system/unix/user.cr

@@ -15,9 +15,9 @@ module Crystal::System::User
     username.check_no_null_byte
 
     pwd = uninitialized LibC::Passwd
-    pwd_pointer = pointerof(pwd)
+    pwd_pointer = Pointer(LibC::Passwd).null
     System.retry_with_buffer("getpwnam_r", GETPW_R_SIZE_MAX) do |buf|
-      LibC.getpwnam_r(username, pwd_pointer, buf, buf.size, pointerof(pwd_pointer)).tap do
+      LibC.getpwnam_r(username, pointerof(pwd), buf, buf.size, pointerof(pwd_pointer)).tap do
         # It's not necessary to check success with `ret == 0` because `pwd_pointer` will be NULL on failure
         return from_struct(pwd) if pwd_pointer
       end
@@ -29,9 +29,9 @@ module Crystal::System::User
     return unless id
 
     pwd = uninitialized LibC::Passwd
-    pwd_pointer = pointerof(pwd)
+    pwd_pointer = Pointer(LibC::Passwd).null
     System.retry_with_buffer("getpwuid_r", GETPW_R_SIZE_MAX) do |buf|
-      LibC.getpwuid_r(id, pwd_pointer, buf, buf.size, pointerof(pwd_pointer)).tap do
+      LibC.getpwuid_r(id, pointerof(pwd), buf, buf.size, pointerof(pwd_pointer)).tap do
         # It's not necessary to check success with `ret == 0` because `pwd_pointer` will be NULL on failure
         return from_struct(pwd) if pwd_pointer
       end