From: Thomas Weißschuh thomas.weissschuh@linutronix.de
[ Upstream commit e5407c0820ea5fa7117b85ed32b724af73156d63 ]
The printf format checking in the compiler uses the intmax types from the compiler, not libc. This can lead to compiler errors.
Instead use the types already provided by the compiler.
Example issue with clang 19 for arm64:
nolibc-test.c:30:2: error: format specifies type 'uintmax_t' (aka 'unsigned long') but the argument has type 'uintmax_t' (aka 'unsigned long long') [-Werror,-Wformat]
Signed-off-by: Thomas Weißschuh thomas.weissschuh@linutronix.de Acked-by: Willy Tarreau w@1wt.eu Signed-off-by: Sasha Levin sashal@kernel.org ---
**YES** This commit should be backported to stable kernel trees. Here's my extensive analysis: ## Analysis of the Code Changes The commit makes a targeted fix to resolve compiler format checking errors by changing the intmax type definitions in `tools/include/nolibc/stdint.h`: ```c -typedef int64_t intmax_t; -typedef uint64_t uintmax_t; +typedef __INTMAX_TYPE__ intmax_t; +typedef __UINTMAX_TYPE__ uintmax_t; ``` ## Why This Should Be Backported ### 1. **Fixes Real Compilation Errors** The commit addresses actual compiler errors that prevent successful builds, as demonstrated by the clang 19 error message: ``` nolibc- test.c:30:2: error: format specifies type 'uintmax_t' (aka 'unsigned long') but the argument has type 'uintmax_t' (aka 'unsigned long long') [-Werror,-Wformat] ``` This is a critical build breakage, not just a warning. ### 2. **Small, Contained, Low-Risk Change** - Only changes 2 lines of code in a single header file - Does not modify any algorithms or control flow - Uses well-established compiler built-ins that have been available for decades - No risk of behavioral changes beyond fixing the type compatibility issue ### 3. **Follows Established Pattern** The change aligns with existing practice in the same file, which already uses `__SIZE_TYPE__` for `size_t` definition. This demonstrates that using compiler built-ins for fundamental types is the established approach in nolibc. ### 4. **Cross-Platform Compatibility Fix** The issue particularly affects: - Different compiler backends (GCC vs Clang) - Different architectures where `long` vs `long long` sizes vary (especially arm64) - Cross-compilation scenarios - Builds with strict format checking enabled (`-Wformat -Werror`) ### 5. **Comparison with Similar Commits** Looking at the reference commits provided: - **Similar Commit #4** (Status: YES): Also fixes integer type issues in nolibc for platform compatibility - **Similar Commit #5** (Status: YES): Also fixes printf format mismatches with explicit stable tree marking (`Cc: stable@vger.kernel.org`) This commit follows the same pattern of fixing type/format compatibility issues that have been deemed worthy of backporting. ### 6. **Tools Subsystem Stability** While this is in the tools directory, nolibc is used for: - Kernel testing infrastructure - Minimal userspace environments - Cross-compilation toolchains - Kernel selftests Breaking builds in these contexts can impact kernel development workflows across different platforms. ### 7. **No Architectural Changes** The commit: - Doesn't introduce new features - Doesn't change APIs - Doesn't modify kernel core functionality - Simply ensures type consistency between compiler and library definitions ## Conclusion This is exactly the type of targeted bug fix that stable trees are designed for: it fixes a real compilation issue that affects users, uses a minimal and safe approach, follows established patterns, and has no risk of introducing regressions. The fix ensures that nolibc can be compiled successfully across different compiler/architecture combinations, which is essential for kernel development infrastructure.
tools/include/nolibc/stdint.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/include/nolibc/stdint.h b/tools/include/nolibc/stdint.h index 6665e272e2132..87a2b09e2dda5 100644 --- a/tools/include/nolibc/stdint.h +++ b/tools/include/nolibc/stdint.h @@ -39,8 +39,8 @@ typedef size_t uint_fast32_t; typedef int64_t int_fast64_t; typedef uint64_t uint_fast64_t;
-typedef int64_t intmax_t; -typedef uint64_t uintmax_t; +typedef __INTMAX_TYPE__ intmax_t; +typedef __UINTMAX_TYPE__ uintmax_t;
/* limits of integral types */