Fix some compiler warning about unaligned access - #197
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Thanks @mhei for these changes. I added a couple minor comments in the review. At least on GCC 14.2 the compiler is smart enough to not warn about taking the address of a packed structure member if it is immediately converted into a |
Serialize variable-length VLAN items through a byte buffer instead of taking an aligned struct pointer to a packed message member. GCC does not warn when a packed member address is immediately converted to void * or uint8_t *, and that conversion is safe while the address remains byte-oriented. Merely casting the original struct item pointer through void *, however, would only hide the warning: the following uint16_t member stores could still be unaligned. Use a direct uint8_t * conversion for locating the output and use memcpy to serialize the multi-byte fields without aligned typed accesses. Signed-off-by: Michael Heimpold <mhei@heimpold.de>
Populate the slave bitmap in aligned storage before copying it into the packed MDU traffic statistics request. GCC does not warn when the packed member is passed directly to memcpy because its address is converted to void *, and this is safe for a byte-wise copy. Passing the same address through void * to set32bitmap() would only hide the warning: the function ultimately accesses it as uint32_t *, while the bitmap starts at an address that is not guaranteed to have the required alignment. So use an aligned temporary variable for set32bitmap() and use the packed member directly as the memcpy destination. Signed-off-by: Michael Heimpold <mhei@heimpold.de>
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Oh, it seems that I dont see the comments already...
This is a good point, thanks for pointing out. This makes the patch a little bit simpler and thus easier to read, but the main problem persists. I will force-push a revised version and elaborate in the commit messages... |
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This PR reworks some access to members in packed structs.