I previously blogged about a way to force ltrace to show some shared memory trace records that didn’t show up by default.

Where that fails to be useful, is when you don’t have a guess about what shared library the code in question lives in. I just blundered on the latrace command that uses a Linux dynamic loader audit facility to give a complete trace of all the function-name/library-name pairs that are executed!

Here’s an example invocation:

[sourcecode language=”bash”]
latrace \
clang xx.c -c 2>&1 | c++filt
[/sourcecode]

without output like:

...
 9022     std::operator&(std::memory_order, std::__memory_order_modifier) [/home/pjoot/clang/be.5e0ac1f.lz31/bin/../lib/libLLVMAnalysis.so]
 9022     std::operator&(std::memory_order, std::__memory_order_modifier) [/home/pjoot/clang/be.5e0ac1f.lz31/bin/../lib/libLLVMAnalysis.so]
 9022     strlen [/lib64/libc.so.6]
 9022     strlen [/lib64/libc.so.6]
 9022     strlen [/lib64/libc.so.6]
 9022     llvm::cl::basic_parser::basic_parser(llvm::cl::Option&) [/home/pjoot/clang/be.5e0ac1f.lz31/bin/../lib/libLLVMSupport.so]
 9022     strlen [/lib64/libc.so.6]
 9022     llvm::cl::Option::setArgStr(llvm::StringRef) [/home/pjoot/clang/be.5e0ac1f.lz31/bin/../lib/libLLVMSupport.so]
 9022     strlen [/lib64/libc.so.6]
 9022     std::pair::__type, std::__decay_and_strip::__type> std::make_pair(void const**&&, bool&&) [/home/pjoot/clang/be.5e0ac1f.lz31/bin/../lib/libLLVMX86CodeGen.so]
 9022       void const**&& std::forward(std::remove_reference::type&) [/home/pjoot/clang/be.5e0ac1f.lz31/bin/../lib/libLLVMX86CodeGen.so]
 9022       bool&& std::forward(std::remove_reference::type&) []
 9022       void const**&& std::forward(std::remove_reference::type&) [/home/pjoot/clang/be.5e0ac1f.lz31/bin/../lib/libLLVMX86CodeGen.so]
 9022       bool&& std::forward(std::remove_reference::type&) []
 9022     void const**&& std::forward(std::remove_reference::type&) [/home/pjoot/clang/be.5e0ac1f.lz31/bin/../lib/libLLVMX86CodeGen.so]
...

With this latrace command, we get all the shared library function call names and their corresponding shared library names. Using that info we can dig into a specific shared library with ltrace or the debugger, once a point of interest is determined.