[ATfE] Document _platform_debug_putc()#723
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voltur01 merged 2 commits intoarm:arm-softwarefrom Feb 19, 2026
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Add more details about `void _platform_debug_putc(int c)` to the documentation page.
smithp35
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Feb 11, 2026
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One small suggestion, which I don't think is necessary if you prefer the original. Otherwise looks good to me.
| With `crt0` the output is discarded. You can implement | ||
| `void _platform_debug_putc(int c)` in your application to redirect it, | ||
| for example, to an UART. The implementation must be safe to be called with | ||
| only the assumption that the stack pointer is setup: it must not use heap or |
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On the assumption that this may be called before we copy code and data from flash to RAM could be worth mentioning that. Possibly:
it must not use the heap or call other LLVM libc functions. It must not access any code or data that depends on _platform_init_data_segments().
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Really good point, thanks - added!
MarkMurrayARM
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Feb 11, 2026
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@MarkMurrayARM could you please re-review, thank you! |
voltur01
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Feb 20, 2026
Add more details about `void _platform_debug_putc(int c)` to the documentation page.
voltur01
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Feb 20, 2026
This cherry-picks changes relevant to llvmlibc-support from current arm-software into the 22.x release branch: 12a4f2c [ATfE] Document _platform_debug_putc() (#723) 75faad2 [ATfE] Support command line options in LLVM libc (#705) 2ae2b6c [ATfE] Fix libc v7-R no-fpregs attribute build failure (#720) bc8a58b [ATfE] Provide LLVM libc handlers for hardware and runtime setup (#706) 852e751 [ATfE] Provide debug output handler in LLVM libc crt0 9be5d72 (origin/add_unhosted_exit, add_unhosted_exit) Simplified implementation of exit to avoid issues with privileged assembly instructions 983f37c [ATfE] Provide nohost init and exit in llvmlibc startup code 6859f67 [ATfE] Replace call to abort with __llvm_libc_exit in libc startup code (#678) a284205 (origin/update_exit_comment, update_exit_comment) [ATfE] Update comment about handling cleanup for exit() fb865b8 (origin/remove_abort_redefinition, remove_abort_redefinition) [ATfE] Replace call to abort with __llvm_libc_exit in libc startup code 28c43df (origin/use_sys_readc_for_stdin) Merge branch 'arm-software' into use_sys_readc_for_stdin 53e062f (use_sys_readc_for_stdin) Added a comment with rationale and TODO bbf19b6 (origin/add_semihosting_abort, add_semihosting_abort) Mark internal semihosting function as static 52d1d90 Provide semihosting_call_exit() and add TODO for exit() 99c608d Replace exit() with direct call to __llvm_libc_exit() 07fe14b [ATfE] Use semihosting SYS_READC for stdin with llvm libc ab08655 [ATfE] Redirect libc abort() to semihosting exit()
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Add more details about
void _platform_debug_putc(int c)to the documentation page.