Debugging Tools

Building with Debug flags

When profiling or debugging, it is normally necessary to pass -g or other flags to cause the compiler to emit debugging symbols. CMake uses a build type to control the compiler flags used for optimization and debugging. The CMAKE_BUILD_TYPE variable is used to set the build type.

Currently the following build types are supported by the JEDI ecbuild bundles:

• CMAKE_BUILD_TYPE=Release: Optimized for performance, disables all debugging options. [Default]

• CMAKE_BUILD_TYPE=Debug: Enables debugging and sanitizer options that incur significant performance overhead.

If no build type is specified the Release build type will be used. Only use the Debug build type when testing or debugging non-performance related issues, as it will significantly effect performance.

To add -g and other debugging flags to the Release builds, set the following environment variables, and the remove the build directory and rebuild the bundle completely:

export CFLAGS="-g"
export CXXFLAGS="-g"
export FFLAGS="-g"
export LDFLAGS="-Wl,-z,now"

Note

The LDFLAGS="-Wl,-z,now flag is recommended when debugging or profiling. From man ld, the -z now option had the following effect:

When generating an executable or shared library, mark it to tell the dynamic linker to resolve all symbols when the program is started, or when the shared library is linked to using dlopen, instead of deferring function call resolution to the point when the function is first called.

Allowing the default behavior of -z lazy can confuse debuggers and performance profilers, as symbol resolution and dynamic library loading will occur during debugging.