Re: [cmake-developers] RFC: LLVM community CMake documentation

[Chris Bieneman]

Thank you everyone for the feedback!

I’ve updated the document based on the feedback.

In addition to this document I’m also working on putting together a set of 
coding standards/guidelines/tips that are more LLVM-specific. When I get that 
together I’ll also send it over here for feedback.

The only comment I think I didn’t directly update the document for was Dan’s 
comment about GLOBAL properties. I kinda have mixed feelings about GLOBAL 
properties. I know why we use them, but I’m not sure I want to encourage people 
to use them. I think some of the places we use them is just wrong.

Many thanks!
-Chris



CMakePrimer.rst
Description: Binary data


> On Apr 27, 2016, at 1:39 PM, Chris Bieneman  wrote:
> 
> Hello cmake-developers,
> 
> Earlier this year the LLVM community finished migrating to CMake as our one 
> and only build system. One of the lingering things on my to-do list to help 
> this transition is to write some basic documentation for the CMake language 
> to help LLVM developers get a feel for the language.
> 
> I’ve attached the working draft of my documentation, and would greatly 
> appreciate any feedback from members of the CMake community. While it is not 
> my goal to be a definitive source, I would like to be as accurate as I can be.
> 
> Thank you,
> -Chris
> 
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Re: [cmake-developers] [CMake 0016082]: Support alternative download URL in ExternalProject_Add

[A. Klitzing]

Hi there!

I added that feature in the attached patch.

Best regards
   André Klitzing
From 856b9e78b00180a232d4b9d498a726489778a07d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9=20Klitzing?= 
Date: Thu, 28 Apr 2016 21:03:26 +0200
Subject: [PATCH] Add support for multiple/alternative URLs

Now it is possible to pass multiple URLs as a list
that will be tried in and foreach(). So it will
try next URL if the previous failed.

ExternalProject_Add(dummy
URL "${FIRST_URL}" "${SECOND_URL}" "${THIRD_URL}"
)
---
 Modules/ExternalProject.cmake | 23 +--
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/Modules/ExternalProject.cmake b/Modules/ExternalProject.cmake
index 9cc8a20..7e68b30 100644
--- a/Modules/ExternalProject.cmake
+++ b/Modules/ExternalProject.cmake
@@ -69,8 +69,8 @@ Create custom targets to build projects in external trees
 URL of mercurial repo
   ``HG_TAG ``
 Mercurial branch name, commit id or tag
-  ``URL /.../src.tgz``
-Full path or URL of source
+  ``URL /.../src.tgz /other/path/src.tgz``
+Full pathes or URLs of source.
   ``URL_HASH ALGO=value``
 Hash of file at URL
   ``URL_MD5 md5``
@@ -901,8 +901,10 @@ function(_ep_write_downloadfile_script script_filename remote local timeout no_p
   endif()
 
   file(WRITE ${script_filename}
-"${hash_check}message(STATUS \"downloading...
- src='${remote}'
+"${hash_check}
+foreach(url ${remote})
+ message(STATUS \"downloading...
+ src='\${url}'
  dst='${local}'
  timeout='${timeout_msg}'\")
 
@@ -910,7 +912,7 @@ ${tls_verify_code}
 ${tls_cainfo_code}
 
 file(DOWNLOAD
-  \"${remote}\"
+  \"\${url}\"
   \"${local}\"
   ${show_progress}
   ${timeout_args}
@@ -921,13 +923,22 @@ list(GET status 0 status_code)
 list(GET status 1 status_string)
 
 if(NOT status_code EQUAL 0)
-  message(FATAL_ERROR \"error: downloading '${remote}' failed
+  message(WARNING \"downloading '\${url}' failed
   status_code: \${status_code}
   status_string: \${status_string}
   log: \${log}
 \")
 endif()
 
+if(status_code EQUAL 0)
+   break()
+endif()
+endforeach()
+
+if(NOT status_code EQUAL 0)
+   message(FATAL_ERROR \"error: each download failed\")
+endif()
+
 message(STATUS \"downloading... done\")
 "
 )
-- 
2.8.0

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Re: [cmake-developers] RFC: LLVM community CMake documentation

[Dan Liew]

Hi Chris,

Thanks for doing this. I've had a quick scan and I have a few minor comments.

# Scripting overview

This is personal preference but I don't like ``add_definitions()`` due
to its global behaviour so I think its use should be discouraged. I
much prefer ``target_compile_definitions()`` which isn't global.

# Dereferencing

One "Gotcha" I think that is worth mentioning is implicit derefencing
of variables in ``if()`` conditionals

for example

```
if ("${SOME_VAR}" STREQUAL "MSVC")
```

behaves very strangely because CMake will implicitly dereference
"MSVC" (as if it was "${MSVC}") where as someone reading the code
probably thinks that it is trying to check if the contents of the
SOME_VAR as a string are "MSVC".

This behaviour is prevented by setting CMP0054 to NEW but this was
only introduced with CMake 3.1 and I don't think that's LLVM's minimum
version so developers might hit this issue. Run ``cmake --help-policy
CMP0054`` for more details.

A hacky work around I employ is to write conditionals like that like this

```
if ("X${SOME_VAR}" STREQUAL "XMSVC")
```

It's not good though...

# Scope

You don't mention "GLOBAL" properties. IIRC LLVM's CMake code uses
these so it might be worth mentioning these

# LLVM specific macros/functions

LLVM's CMake code pretty much avoids using many of the standard CMake
commands for declaring targets favouring its own (sometimes
confusingly named, e.g. add_llvm_library Vs. llvm_add_library) which I
sometime find quite confusing. Seeing as this guide is aimed at LLVM
developers I think this document (or an accompanying document) should
describe these macros/functions.

Thanks,
Dan.
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Re: [cmake-developers] RFC: LLVM community CMake documentation

[Chuck Atkins]

Hi Chris,

This is great!  I do have a suggestion that perhaps Brad could weigh in on
(may disagree).  Since your already looking at a reasonably recent minimum
requirement in your examples (3.2) and discussing bumping the minimum up to
3.4.3 even, I think it would be worthwhile to let even some of the simple
examples show some of the newer language features and syntax.  For example,
in your lists of lists example, you currently have:

foreach(list_name ${list_of_lists})
  foreach(value ${${list_name}})
message(${value})
  endforeach()
endforeach()

which has been valid CMake syntax since the days of yore, but you could
show the newer syntax instead that uses the list variables directly instead
of de-referencing them:

foreach(list_name IN LISTS list_of_lists)
  foreach(value IN LISTS ${list_name})
message(${value})
  endforeach()
endforeach()

It's of course a preference for how you want to document and use CMake in
llvm but it might be good to get users started right off the bat with "new"
cmake.


- Chuck

On Wed, Apr 27, 2016 at 4:39 PM, Chris Bieneman 
wrote:

> Hello cmake-developers,
>
> Earlier this year the LLVM community finished migrating to CMake as our
> one and only build system. One of the lingering things on my to-do list to
> help this transition is to write some basic documentation for the CMake
> language to help LLVM developers get a feel for the language.
>
> I’ve attached the working draft of my documentation, and would greatly
> appreciate any feedback from members of the CMake community. While it is
> not my goal to be a definitive source, I would like to be as accurate as I
> can be.
>
> Thank you,
> -Chris
>
>
> --
>
> Powered by www.kitware.com
>
> Please keep messages on-topic and check the CMake FAQ at:
> http://www.cmake.org/Wiki/CMake_FAQ
>
> Kitware offers various services to support the CMake community. For more
> information on each offering, please visit:
>
> CMake Support: http://cmake.org/cmake/help/support.html
> CMake Consulting: http://cmake.org/cmake/help/consulting.html
> CMake Training Courses: http://cmake.org/cmake/help/training.html
>
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> http://www.kitware.com/opensource/opensource.html
>
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>
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Re: [cmake-developers] Code style auto-formatting

[Brad King]

On 04/27/2016 07:12 PM, Daniel Pfeifer wrote:
> It took a while, but i figured out .clang-format definitions (there
> are two required) and a script that, after applying, does not break
> compilation and unit tests.

Thanks!  I'll try that out myself when I get a chance.

> I have attached a patch that adds the .clang-format and two other
> patches that need to be applied before reformatting.

Meanwhile I've applied these cleanups:

 CursesDialog: add missing cmState include
 https://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=bb8fdcf6

 Tests: add blank line between includes in StringFileTest
 https://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=29abee03

-Brad

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Re: [cmake-developers] Integration of clang-tidy

[Brad King]

On 04/27/2016 06:48 PM, Daniel Pfeifer wrote:
> It is unrelated. Clang-Tidy picks the interesting pieces from the
> compiler command line and ignores the rest. Whether cc is given or not
> makes no difference.
> But maybe we should leave the decision what to pick to Clang-Tidy? It
> may be clearer to forward the original command line unmodified.

Applied, thanks!

 Clang-Tidy: Give entire compiler command line to clant-tidy tool
 https://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=304ab71d

-Brad

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Re: [cmake-developers] RFC: LLVM community CMake documentation

[Brad King]

On 04/27/2016 04:39 PM, Chris Bieneman wrote:
> attached the working draft of my documentation

Good work!  Most of it looks great.  Here are minor some comments.

Please add a link to the cmake-language(7) manual:

  https://cmake.org/cmake/help/v3.5/manual/cmake-language.7.html

somewhere.  It has a lot of useful information, though is more of a
reference than an introduction.  It also has a formal grammar.

> .. code-block:: console
> 
>cmake_minimum_required(VERSION 3.2)

I think you can specify "cmake" as the code block language here.
CMake uses rst/sphinx for our docs and we do this frequently.

> One of the few examples is PATH variables, which CMake does have some special
> handling for.

This special handling is for both PATH and FILEPATH and is explained
at the end of this section:

 https://cmake.org/cmake/help/v3.5/command/set.html#set-cache-entry

> CMake provides a module `CMakeParseArguments` which provides an implementation
> of advanced argument parsing.

FYI, in CMake 3.5 and above cmake_parse_arguments is a native command:

 https://cmake.org/cmake/help/v3.5/command/cmake_parse_arguments.html

and the CMakeParseArguments module is an empty placeholder for compatibility.

-Brad

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[cmake-developers] [CMake 0016086]: Ninja generator doesn't handle multiple Mac apps using the same plist file with MACOSX_BUNDLE_INFO_PLIST

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
== 
https://cmake.org/Bug/view.php?id=16086 
== 
Reported By:Florent Castelli
Assigned To:
== 
Project:CMake
Issue ID:   16086
Category:   CMake
Reproducibility:always
Severity:   major
Priority:   normal
Status: new
== 
Date Submitted: 2016-04-28 05:37 EDT
Last Modified:  2016-04-28 05:37 EDT
== 
Summary:Ninja generator doesn't handle multiple Mac apps
using the same plist file with MACOSX_BUNDLE_INFO_PLIST
Description: 
If an app is using the same plist file using the target property
MACOSX_BUNDLE_INFO_PLIST, CMake will add a dependency on that plist file as it
is a template with variables that needs processing at generation time.

But if multiple apps are using the same plist template, CMake will add multiple
dependencies to the same file on the Re-Run target and Ninja will then warn:
ninja: warning: multiple rules generate ../Info.plist.in. builds involving this
target will not be correct; continuing anyway [-w dupbuild=warn]

A fix would probably be to deduplicate the dependencies for rerunning CMake.
== 

Issue History 
Date ModifiedUsername   FieldChange   
== 
2016-04-28 05:37 Florent CastelliNew Issue
==

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