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pasko-zh / brzo_i2c

Brzo I2C is a fast I2C Implementation written in Assembly for the esp8266
GNU General Public License v3.0
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Enabling -Wall GCC option shows some warnings #22

Closed valkuc closed 6 years ago

valkuc commented 6 years ago

I'm not familar with assembler, please check either those variables are used or can be safely removed:

'a_bit_index' is used uninitialized in this function [-Wuninitialized]  brzo_i2c.c  line 768
'a_bit_index' may be used uninitialized in this function [-Wmaybe-uninitialized]    brzo_i2c.c  line 73
'a_bit_index' may be used uninitialized in this function [-Wmaybe-uninitialized]    brzo_i2c.c  line 389
'a_in_value' is used uninitialized in this function [-Wuninitialized]   brzo_i2c.c  line 768
'a_in_value' may be used uninitialized in this function [-Wmaybe-uninitialized] brzo_i2c.c  line 73
'a_in_value' may be used uninitialized in this function [-Wmaybe-uninitialized] brzo_i2c.c  line 389
'a_set' is used uninitialized in this function [-Wuninitialized]    brzo_i2c.c  line 768
'a_set' is used uninitialized in this function [-Wuninitialized]    brzo_i2c.c  line 1082
'a_set' may be used uninitialized in this function [-Wmaybe-uninitialized]  brzo_i2c.c  line 73
'a_set' may be used uninitialized in this function [-Wmaybe-uninitialized]  brzo_i2c.c  line 389
'a_temp1' is used uninitialized in this function [-Wuninitialized]  brzo_i2c.c  line 768
'a_temp1' is used uninitialized in this function [-Wuninitialized]  brzo_i2c.c  line 1082
'a_temp1' may be used uninitialized in this function [-Wmaybe-uninitialized]    brzo_i2c.c  line 73
'a_temp1' may be used uninitialized in this function [-Wmaybe-uninitialized]    brzo_i2c.c  line 389
pasko-zh commented 6 years ago

These variables are only needed for the inline assembler. They are on the "clobber list": This means, you can set an alias variable name that you can use in the inline assembly. For instance, a_temp1 can be referred to as r_temp1 in the inline assembly.

The "downside" is that if you want to use variables in inline assembly instead of registers, you have to do it this way. And the compiler may give you these warnings, because in the rest of the C code these variable are not used.

The advantage is that the compiler will then replace these variables, e.g., r_temp1, in an optimal way with real registers.

valkuc commented 6 years ago

Ok, no problem!