Cross-compilation with Android API 28

[roderick-koehle]

Bug report

• Operating System:
  • Android NDK r19
  • ANDROID_ABI=x86,armeabi-7a, arm64-v8a
  • ANDROID_TOOLCHAIN_NAME=arm-linux-androideabi-clang
  • ANDROID_NATIVE_API_LEVEL=android-28
• Installation type:
  • Source
• Version or commit hash:
  • master
• DDS implementation:
  • Fast-RTPS
• Client library (if applicable):
  • rclcpp

Steps to reproduce issue

Android cross compilation with latest platform API results in a compile error in the signal_handler of rclcpp.

Actual behavior

Starting >>> rclcpp
--- stderr: rclcpp
/home/EU/dekoehlr/work/ros2_core_ws/src/ros2/rclcpp/rclcpp/src/rclcpp/signal_handler.cpp:176:7: 
error: cannot initialize a variable of type 'int' with an rvalue of type 'char *'
   int error_status = strerror_r(errnum, buffer, buffer_length);
       ^              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
make[2]: *** [CMakeFiles/rclcpp.dir/src/rclcpp/signal_handler.cpp.o] Error 1
make[1]: *** [CMakeFiles/rclcpp.dir/all] Error 2
make: *** [all] Error 2
---
Failed   <<< rclcpp     [ Exited with code 2 ]

Additional information

The cause is the use of the reentrant strerror_r reporting function, which has a inconsistent function signature in the XSI and GNU string.h core library.
The feature test macros (see https://linux.die.net/man/3/strerror_r) to distinguish between XSI and POSIX are not reliable on Android as the _GNU_SOURCE may or may not be defined depending on the API level. For a discussion of the use of strerror_r see http://austingroupbugs.net/view.php?id=655.

Possible solutions are substituting the ambiguous strerror_r by the (re-entrant) strerror_l, or use the prototype definition check provided by cmake, e.g.:

# Query platform depended string functions
check_prototype_definition(strerror_r
  "int strerror_r(int errnum, char *strerrbuf, size_t buflen)"
  "0"
  "string.h"
  XSI_STRERROR_R)
check_prototype_definition(strerror_r
  "char *strerror_r(int errnum, char *buf, size_t buflen)"
  "NULL"
  "string.h"
  GNU_STRERROR_R)
if(XSI_STRERROR_R)
   add_compile_options(-DXSI_STRERROR_R)
endif()
if(GNU_STRERROR_R)
   add_compile_options(-DGNU_STRERROR_R)
endif()

[dirk-thomas]

Please consider to provide a pull request to address this since you have the platform at hand to verify that the potential patch will resolve the problem.

[roderick-koehle]

I submitted pull request #742, with a minimalist approach.

[nuclearsandwich]

@roderick-koehle with #742 merged I am going to close this issue. If there are other issues with cross-compilation we can re-open this one or you can submit a new one as appropriate.