Error in C++ message auto generation in ROS groovy

[drdas]

If a comment description line in a .msg file (starting with #) ends in a a special character such as ( ), extra newlines are added in the generated header file which gives compiler errors when included. Example below:

# ICD-XXXXX - Delta Position
# Primary Measurement: Change in position over a time interval (1D, 2D, or 3D)
# Standard Header
Header header 
#1, 2, or 3 elements based on dimension specified in metadata
float64[] delta_pos
# Delta position covariance matrix (row-major) in [units^2] of size nDim x nDim.
# The matrix is linearized into a single array for storage.
float64[]  delta_pos_covariance

generates the header with the following code (note the extra newlines):

template<class ContainerAllocator>
struct Definition< ::MyClass::DeltaPosition_<ContainerAllocator> >
{
  static const char* value()
  {
    return "# ICD-XXXXX - Delta Position
\n\
# Primary Measurement: Change in position over a time interval (1D, 2D, or 3D)
\n\

\n\
# Standard Header
\n\
Header header

[tfoote]

@drdas see the markdown notation link at the top right of the comment box for how to properly quote code.

[jarvisschultz]

I was just answering this question on answers.ros.org, and noticed that line endings used in the *.msg files can also break the generated C++ header files. For example, consider a simple message file

Header header

If it has only a "\n" line ending, the return string starts with

    return "Header header\n\

But if it ends in "\r\n" the return string starts with

    return "Header header
\n\

Github parses the extra \r in the second one as a carriage return. A hexdump of the two strings reveals that there is indeed an extra 0x0d character in the second string.

This produces compilation errors like

/home/jarvis/groovyws/devel/include/pend_tracker/Pose2DArray.h:174:5: error: missing terminating " character
/home/jarvis/groovyws/devel/include/pend_tracker/Pose2DArray.h:175:1: error: stray ‘\’ in program
/home/jarvis/groovyws/devel/include/pend_tracker/Pose2DArray.h:175:1: error: stray ‘\’ in program
/home/jarvis/groovyws/devel/include/pend_tracker/Pose2DArray.h:175:1: error: stray ‘\’ in program
/home/jarvis/groovyws/devel/include/pend_tracker/Pose2DArray.h:175:1: error: stray ‘\’ in program
/home/jarvis/groovyws/devel/include/pend_tracker/Pose2DArray.h:175:1: error: stray ‘\’ in program
/home/jarvis/groovyws/devel/include/pend_tracker/Pose2DArray.h:175:1: error: stray ‘#’ in program

I tested this with rosbuild and catkin, and got the same results on both.

[dirk-thomas]

I could not reproduce any of the described issues based on the descriptions above. Please provide a file which exhibits the problem for you.

[jarvisschultz]

I was actually also unable to reproduce the error of the error of @drdas. But I am consistently getting the error with the line endings. I just created a gist repo that contains two message files one with \r\n and one with \n. That repo can be cloned here. I also put the header files that are generated for each of the message files and a .gitattributes file that prevents git from changing any line endings.

I may not have made this clear, but the compilation error doesn't show up until you try to #include the generated *.h files in a *.cpp file. To that end, I also put two minimal C++ files and a simple makefile in the repo. Running make work produces a binary with no warnings, and running make broken produces the errors I am seeing.

Here is the hexdump showing the difference between the two files:

jarvis@vedauwoo:~/Desktop/a242acf30b08cfe7d1f3$ hexdump -C works_test.msg
00000000  48 65 61 64 65 72 20 68  65 61 64 65 72 0a        |Header header.|
0000000e
jarvis@vedauwoo:~/Desktop/a242acf30b08cfe7d1f3$ hexdump -C broken_test.msg
00000000  48 65 61 64 65 72 20 68  65 61 64 65 72 0d 0a     |Header header..|
0000000f

Here is the hexdump of the sole differing line in the headers:

jarvis@vedauwoo:~/Desktop/a242acf30b08cfe7d1f3$ sed -n '174p' works_test.h |hexdump -C
00000000  20 20 20 20 72 65 74 75  72 6e 20 22 48 65 61 64  |    return "Head|
00000010  65 72 20 68 65 61 64 65  72 5c 6e 5c 0a           |er header\n\.|
0000001d
jarvis@vedauwoo:~/Desktop/a242acf30b08cfe7d1f3$ sed -n '174p' broken_test.h |hexdump -C
00000000  20 20 20 20 72 65 74 75  72 6e 20 22 48 65 61 64  |    return "Head|
00000010  65 72 20 68 65 61 64 65  72 0d 5c 6e 5c 0a        |er header.\n\.|
0000001e

[dirk-thomas]

Until the fix has been release as a workaround just make sure to save the message file with linux line ending (\n).

[jarvisschultz]

Ridiculously simple fix. I should have looked at the source before bothering to write all of the debug info. Thanks for the fast response!