| ??? 03/28/05 15:01 Read: times Msg Score: +1 +1 Good Answer/Helpful |
#90544 - Clarification Responding to: ???'s previous message |
Ian Bell said:
Donald Catto said:
That particular article refers to a char being compared with an integer. There's nothing surprising about the char being promoted to an integer before comparison.
It refers to a char being compared to a constant, 0XC5 in the example, and failing the comparison because char is signed and therefore is promoted to int before the comparison. If an unsigned char had been used the comparison would have worked becuase integer promotion would not take place. The char is not promoted because it is signed: the promotion occurs because two different types are being compared, where one of those two types cannot represent the value of the other, hence the promotion. Had the char been unsigned the comparison would have worked because 0xc5 fits into an unsigned char. The point I am trying to make is that the signedness is not the important issue. This sort of behaviour can easily trap the inexperienced embedded C programmer which is why I prefer to code such operations in assembler. The same applies to the inexperienced assembler programmer. In all but trivial cases you have to understand the language you are programming in and the platform you are programming on. |
| Topic | Author | Date |
| 8051 in C or assembly? | 01/01/70 00:00 | |
| Probably C | 01/01/70 00:00 | |
| Always C | 01/01/70 00:00 | |
| Mostly 'C' | 01/01/70 00:00 | |
| No magic wand | 01/01/70 00:00 | |
| Assembler when? | 01/01/70 00:00 | |
| Shared data problem?? | 01/01/70 00:00 | |
| Shared Data Problem | 01/01/70 00:00 | |
| I see | 01/01/70 00:00 | |
| Sared Data | 01/01/70 00:00 | |
| addendum | 01/01/70 00:00 | |
| Shared Data | 01/01/70 00:00 | |
| Knowledge, not language. | 01/01/70 00:00 | |
| Knowledge | 01/01/70 00:00 | |
| Knowledge | 01/01/70 00:00 | |
| Promotion | 01/01/70 00:00 | |
| Promotion | 01/01/70 00:00 | |
| Promotion | 01/01/70 00:00 | |
| Traps for the unwary | 01/01/70 00:00 | |
| Preaching | 01/01/70 00:00 | |
| Ditto | 01/01/70 00:00 | |
| red rag.... | 01/01/70 00:00 | |
Bend over then... | 01/01/70 00:00 | |
| hauling assembler | 01/01/70 00:00 | |
| Clarification | 01/01/70 00:00 | |
| Keil Allows this to be disabled | 01/01/70 00:00 | |
| Know your tools | 01/01/70 00:00 | |
| It means 8 bit may be 16 bits | 01/01/70 00:00 | |
| More knowledge! | 01/01/70 00:00 | |
| not really | 01/01/70 00:00 | |
| So which... | 01/01/70 00:00 | |
| Calculations in C | 01/01/70 00:00 | |
| ibid | 01/01/70 00:00 | |
| Not always.. | 01/01/70 00:00 | |
| Example | 01/01/70 00:00 | |
| Better?? | 01/01/70 00:00 | |
| assembly | 01/01/70 00:00 | |
| YMMV | 01/01/70 00:00 | |
| assembly | 01/01/70 00:00 | |
| Hitting the Wall | 01/01/70 00:00 |