script: footprint: Improve C++ static variable reporting #96573
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Enhance the `size_report` script to correctly categorize static C++ variables in the memory report. Static C++ variables are currently listed under the "No paths" category in the size report. This occurs because the script's address-based mapping logic is designed for functions, which occupy an address range, but fails to handle variables that have only a single memory address. This commit improves the `do_address_range_matching` function to handle single-address mappings. The updated logic now correctly identifies and assigns static C++ variables to their corresponding source file paths in the report tree, providing a more accurate and comprehensive memory footprint analysis for C++ applications. This enhancement ensures that all symbols, regardless of their linkage or type, are correctly placed in the report, providing a more accurate overview of memory usage. Signed-off-by: Nilesh Vyas <[email protected]>
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script: footprint: Improve C++ static variable reporting
This commit enhances the
size_reportscript to correctly categorize static C++ variables in the memory report tree. Previously, these variables were incorrectly grouped under the "No paths" category.Problem Description
The
size_report.pyscript uses DWARF debug information and ELF symbol tables to map memory usage to source file paths. While this system works well for C and most C++ functions, a specific limitation exists for C++ static variables.DW_TAG_subprogram) are typically defined by an address range (DW_AT_low_pctoDW_AT_high_pc). In contrast, variables (DW_TAG_variable) are represented by a single, specific address (DW_AT_location).This behaviour gives a misleading view of memory usage for C++ applications with static members, as a significant portion of the memory footprint could be incorrectly attributed to the "No paths" section.
Solution
This change introduces a more robust address-based mapping system within the
do_address_range_matchingfunction.DW_TAG_subprogram) and variables (DW_TAG_variable) from the DWARF information.DW_AT_locationaddress.This solution ensures that static C++ variables are correctly mapped to their source files by using the most reliable piece of information available: the memory address. This approach is more robust than name-based matching, as it bypasses C++'s name mangling complexities and handles all symbols based on their location in memory.
Impact
This enhancement provides a more accurate and detailed memory footprint report for C++ applications, allowing developers to better understand and optimize memory usage. Static C++ variables will now be correctly nested under their respective file paths in the report tree, providing a clearer overview of the binary's composition.