Fix 32-bit time_t compile errors in DLTv2 timestamp code#856
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minminlittleshrimp
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Apr 23, 2026
On platforms where time_t is 32-bit (e.g. armv7/musl, glibc arm with default _FILE_OFFSET_BITS), several DLTv2 timestamp call sites trigger -Werror=shift-count-overflow, -Werror=sign-conversion, or -Werror=sign-compare, preventing compilation. Fixes: - ts.tv_sec >> 32 (9 sites in dlt-daemon.c, dlt_daemon_client.c, dlt_client.c, dlt_user.c, dlt_common.c): cast to uint64_t before shifting. On 32-bit time_t the shift is UB; on 64-bit it is a no-op. The top byte of the 40-bit seconds field is now correctly zero on 32-bit platforms instead of carrying a stray duplicate of the low byte (caused by ARM's 5-bit shift-count mask). - time_t tt = msg->storageheader->seconds (dlt_common.c:1084): explicit (time_t) cast to silence sign-conversion when time_t is signed 32-bit. - st.st_size > UINT_MAX (dlt_user.c:5620): cast st.st_size to uintmax_t for the comparison, avoiding the signed/unsigned mismatch between off_t and unsigned int. Signed-off-by: john crosbie <john@excelfore.com>
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Summary
On platforms where
time_tis 32-bit (e.g. armv7 Linux with default_FILE_OFFSET_BITS), several DLTv2 timestamp call sites trigger-Werror=shift-count-overflow,-Werror=sign-conversion, or-Werror=sign-compare, preventing compilation with the-Werrorflags the project sets in its top-levelCMakeLists.txt.Fixes
ts.tv_sec >> 32(9 sites acrossdlt-daemon.c,dlt_daemon_client.c,dlt_client.c,dlt_user.c,dlt_common.c) — castts.tv_sectouint64_tbefore the shift. On 32-bittime_tthe shift was undefined behavior; on ARM it silently wrapped to>> 0due to the 5-bit shift-count mask, which meantseconds[0]in the 40-bit DLTv2 timestamp carried a duplicate of the low byte instead of the expected 0. After the cast the top byte is correctly 0 on 32-bit platforms. No behavior change on 64-bit platforms.time_t tt = msg->storageheader->seconds(dlt_common.c:1084) — explicit(time_t)cast to silence-Wsign-conversionwhentime_tis signed 32-bit andstorageheader->secondsisuint32_t.st.st_size > UINT_MAX(dlt_user.c:5620) — castst.st_sizetouintmax_tfor the comparison to avoid-Wsign-comparebetweenoff_t(signed long) andunsigned int. The precedingst.st_size < 0check still guards the cast.Test plan
dltanddlt-daemonfor armv7 Linux (glibc, 32-bittime_t) with-Werror -Wfatal-errors -Wconversion -Wshadow -Wundef -Wcast-qual— clean build and install.time_t).Supersedes #855 (closed to correct commit authorship).
Author: john@excelfore.com