From b611da43b68193dcb7e632adb44d506374a5d3ef Mon Sep 17 00:00:00 2001 From: Thomas Richter Date: Fri, 27 Jul 2018 10:21:26 +0200 Subject: perf build: Build error in libbpf missing initialization MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In linux-next tree compiling the perf tool with additional make flags EXTRA_CFLAGS="-Wp,-D_FORTIFY_SOURCE=2 -O2" causes a compiler error. It is the warning 'variable may be used uninitialized' which is treated as error: I compile it using a FEDORA 28 installation, my gcc compiler version: gcc (GCC) 8.0.1 20180324 (Red Hat 8.0.1-0.20). The file that causes the error is tools/lib/bpf/libbpf.c. [root@p23lp27] # make V=1 EXTRA_CFLAGS="-Wp,-D_FORTIFY_SOURCE=2 -O2" [...] Makefile.config:849: No openjdk development package found, please install JDK package, e.g. openjdk-8-jdk, java-1.8.0-openjdk-devel Warning: Kernel ABI header at 'tools/include/uapi/linux/if_link.h' differs from latest version at 'include/uapi/linux/if_link.h' CC libbpf.o libbpf.c: In function ‘bpf_perf_event_read_simple’: libbpf.c:2342:6: error: ‘ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized] int ret; ^ cc1: all warnings being treated as errors mv: cannot stat './.libbpf.o.tmp': No such file or directory /home6/tmricht/linux-next/tools/build/Makefile.build:96: recipe for target 'libbpf.o' failed Suggested-by: Jakub Kicinski Signed-off-by: Thomas Richter Signed-off-by: Daniel Borkmann --- tools/lib/bpf/libbpf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'tools') diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index d881d370616c..1aafdbe827fe 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -2273,8 +2273,8 @@ bpf_perf_event_read_simple(void *mem, unsigned long size, volatile struct perf_event_mmap_page *header = mem; __u64 data_tail = header->data_tail; __u64 data_head = header->data_head; + int ret = LIBBPF_PERF_EVENT_ERROR; void *base, *begin, *end; - int ret; asm volatile("" ::: "memory"); /* in real code it should be smp_rmb() */ if (data_head == data_tail) -- cgit v1.2.3