Re: alignment and packed structs
On Wed, 6 Jan 2021, Patrick Welche wrote:
I just tried to compile if_iwn as a module. It failed with
dev/pci/if_iwn.c:2685:6: error: converting a packed 'struct iwn_fw_dump'
pointer (alignment 1) to a 'uint32_t' {aka 'unsigned int'} pointer (alignment
4) may result in an unaligned pointer value [-Werror=address-of-packed-member]
I got around it with
...
Why isn't this necessary when building if_iwn.c as part of a kernel?
This isn't an isolated case. I recently built some other (Intel
DRM) code as modules and had to "fix " the code in 3 or 4 places
for the whole kernel/module compilation to complete successfully.
I figured it was a case of slightly different compiler flags being
used for the monolithic vs. modular kernel builds.
-RVP
alignment and packed structs
I just tried to compile if_iwn as a module. It failed with
dev/pci/if_iwn.c:2685:6: error: converting a packed 'struct iwn_fw_dump'
pointer (alignment 1) to a 'uint32_t' {aka 'unsigned int'} pointer (alignment
4) may result in an unaligned pointer value [-Werror=address-of-packed-member]
I got around it with
diff -u -r1.17 if_iwnreg.h
--- if_iwnreg.h 19 Jul 2017 16:55:12 - 1.17
+++ if_iwnreg.h 6 Jan 2021 17:24:01 -
@@ -1447,7 +1447,7 @@
uint32_tsrc_line;
uint32_ttsf;
uint32_ttime[2];
-} __packed;
+} __attribute__((aligned(4),packed));
/* TLV firmware header. */
struct iwn_fw_tlv_hdr {
Why isn't this necessary when building if_iwn.c as part of a kernel?
Is the above the right solution?
Cheers,
Patrick
