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a9ab562777
When enable DEBUG_BUILD, the perf build failed by the following error:
libbpf.c:727:36: error: 'data' may be used uninitialized in this function [-Werror=maybe-uninitialized]
This is ok until Khem commit a patch in oe-core:
16643b03227466e2c80a24c2d079fe36e89553c1
This commit import "-Og" option to "DEBUG_OPTIMIZATION", result in this error.
Actually, the warning was misinformation. We explore the code in libbpf.c:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/lib/bpf/libbpf.c#n640
--------------------------------------------------------------------------
if (scn)
data = elf_getdata(scn, NULL);
if (!scn || !data) {
pr_warning("failed to get Elf_Data from map section %d\n",
obj->efile.maps_shndx);
return -EINVAL;
}
......
using data...
......
--------------------------------------------------------------------------
If the 'scn' was not null, the data will be initialized. if the data was null,
the function will return -EINVAL, so the data must be not null, but compiler
can't see it in 'if' code block, so treat it as 'maybe-uninitialized'.
(From OE-Core rev: 0eb4048bc5865579327f5a88086e3e3241b012cb)
Signed-off-by: Dengke Du <dengke.du@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
QEMU Emulation Targets ====================== To simplify development, the build system supports building images to work with the QEMU emulator in system emulation mode. Several architectures are currently supported in 32 and 64 bit variants: * ARM (qemuarm + qemuarm64) * x86 (qemux86 + qemux86-64) * PowerPC (qemuppc only) * MIPS (qemumips + qemumips64) Use of the QEMU images is covered in the Yocto Project Reference Manual. The appropriate MACHINE variable value corresponding to the target is given in brackets.