ELF files contain metadata like debug information so their size on disk is not a good indication of the amount of Flash the program will use once it's loaded on the target device's memory.
To display the amount of Flash the program will occupy on the target device use the
cargo-size tool, which is part of the
✅ Use the following command to print the binary's size in system V format.
$ cargo size --bin hello -- -A
Expected output: The breakdown of the program's static memory usage per linker section.
hello : section size addr .vector_table 256 0x0 .text 9740 0x100 .rodata 4568 0x270c .data 8 0x20000000 .bss 2124 0x20000008 .uninit 0 0x20000854
🔎 More details about each linker section:
The first three sections are contiguously located in Flash memory -- Flash memory spans from address
0x0010_0000 (1 MB).
.vector_tablesection contains the vector table, a data structure required by the Cortex-M ISA.
.textsection contains the instructions the program will execute.
.rodatasection contains constants like strings literals.
The next three sections,
.uninit, are located in RAM -- RAM memory spans the address range
0x2004_0000 (256 KB). These sections contain statically allocated variables (
Another other useful tool to analyze the binary size of a program is
$ cargo bloat --bin hello File .text Size Crate Name 0.7% 13.5% 1.3KiB std <char as core::fmt::Debug>::fmt 0.5% 9.6% 928B hello hello::__cortex_m_rt_main 0.4% 8.4% 804B std core::str::slice_error_fail 0.4% 8.0% 768B std core::fmt::Formatter::pad 0.3% 6.4% 614B std core::fmt::num::<impl core::fmt::Debug for usize>::fmt (..) 5.1% 100.0% 9.4KiB .text section size, the file size is 184.5KiB
This breakdowns the size of the
.text section by function. This breakdown can be used to identify the largest functions in the program; those could then be modified to make them smaller.