selftests/bpf: Change variable types for -Wsign-compare #6182
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This is a follow up patch for commit 495d2d8("selftests/bpf: Attempt to build BPF programs with -Wsign-compare") from Alexei Starovoitov[1] to be able to enable -Wsign-compare C compilation flag for clang since -Wall doesn't add it and BPF programs are built with clang.This has the benefit to catch problematic comparisons in future tests as quoted from the commit message:" int i = -1; unsigned int j = 1; if (i < j) // this is false. long i = -1; unsigned int j = 1; if (i < j) // this is true. C standard for reference: - If either operand is unsigned long the other shall be converted to unsigned long. - Otherwise, if one operand is a long int and the other unsigned int, then if a long int can represent all the values of an unsigned int, the unsigned int shall be converted to a long int; otherwise both operands shall be converted to unsigned long int. - Otherwise, if either operand is long, the other shall be converted to long. - Otherwise, if either operand is unsigned, the other shall be converted to unsigned. Unfortunately clang's -Wsign-compare is very noisy. It complains about (s32)a == (u32)b which is safe and doen't have surprising behavior." This specific patch supresses the following warnings when -Wsign-compare is enabled: 1 warning generated. progs/bpf_iter_bpf_percpu_array_map.c:35:16: warning: comparison of integers of different signs: 'int' and 'const volatile __u32' (aka 'const volatile unsigned int') [-Wsign-compare] 35 | for (i = 0; i < num_cpus; i++) { | ~ ^ ~~~~~~~~ 1 warning generated. progs/bpf_qdisc_fifo.c:93:2: warning: comparison of integers of different signs: 'int' and '__u32' (aka 'unsigned int') [-Wsign-compare] 93 | bpf_for(i, 0, sch->q.qlen) { | ^ ~ ~~~~~~~~~~~ Should be noted that many more similar changes are still needed in order to be able to enable the -Wsign-compare flag since -Werror is enabled and would cause compilation of bpf selftests to fail. [1]. Link:torvalds/linux@495d2d8 Signed-off-by: Mehdi Ben Hadj Khelifa <[email protected]>
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Pull request for series with
subject: selftests/bpf: Change variable types for -Wsign-compare
version: 4
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1013549