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user:embedded_c_code_doesn_t_have_to_be_ugly [2020/05/11 18:27] – [5. Globals] Igor Yefmovuser:embedded_c_code_doesn_t_have_to_be_ugly [2022/04/04 23:32] (current) – external edit 127.0.0.1
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 As such (barring external dependencies) I always advise on using the latest stable language standard supported by the toolchain that your organization is comfortable with. And yes, that means that engineers must continually improve their grasp of the language and be on top of the latest stable standard to efficiently take advantage of the improvements provided by that standard. As such (barring external dependencies) I always advise on using the latest stable language standard supported by the toolchain that your organization is comfortable with. And yes, that means that engineers must continually improve their grasp of the language and be on top of the latest stable standard to efficiently take advantage of the improvements provided by that standard.
-==== 3. #define (and const) vs. enum ====+==== 3. #define (and const) vs. enum and magic numbers ====
 So much has been said about the many advantages of pushing as much work as possible away from the preprocessor and into the compiler that is amazes me to still see tons of ''#define'''s in the modern code where language standard features would provide numerous benefits over the plain old text-based code processing that knows nothing of the code structure or the data types used. So much has been said about the many advantages of pushing as much work as possible away from the preprocessor and into the compiler that is amazes me to still see tons of ''#define'''s in the modern code where language standard features would provide numerous benefits over the plain old text-based code processing that knows nothing of the code structure or the data types used.
  
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 <code C>enum{ s2r_uvc_stream_buf_size = s2r_ep_bulk_video_pkts_count * s2r_ep_bulk_video_pkt_size };</code> <code C>enum{ s2r_uvc_stream_buf_size = s2r_ep_bulk_video_pkts_count * s2r_ep_bulk_video_pkt_size };</code>
 +
 +=== Magic numbers ===
 +You know, that kind:
 +<code C>if(interface == 3){</code>
 +
 +Compare that to this code and tell me - which one makes you understand what that code does?
 +<code C>if(interface == s2r_id_audio_stream_ifc){</code>
  
 ==== 4. Bit manipulations vs. structured data ==== ==== 4. Bit manipulations vs. structured data ====
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 ==== 6. Code blocks' nesting ==== ==== 6. Code blocks' nesting ====
 +Somewhat related to the general question of "how many LoC in a function is too many?" this one goes back to gut feeling that cramming all the code into a single function will somehow have positive optimization benefits overall. Let me be clear here: **it doesn't**. That perception is stemming from the fact that function calls in ''C'', while being very cheap, are not zero-overhead operations.
  
 +This perception completely ignores all the advances made in CPU manufacturing in the past 60 years or so((various speculative execution techniques: branch prediction, prefetching, pipelining, value prediction, code and data caching to name a few)).
 +
 +Just write the code in manageable (one-two page length) chunks, packaged as individual functions. And if there really **is** a concern for stack depth you always have the option of inlining those functions((a very often overlooked method to my surprise)).
 +
 +If you have a long-ass ''switch'' statement - make it into a function. If the branches of your ''if'' or ''case'' statements are large - make them into functions. If there's an overgrown block of code that is responsible for one clearly defined operation - make it into a function. If you find yourself writing an ''if'' inside a ''case'' or a similar situation - extract the code block into a function.
 +
 +And as a general rule: if you see a block of code that doesn't fit onto one screen (or your prefrontal cortex, for that matter) - make it into a function!
 +
 +Think of functions as text paragraphs: if you read some text that consists of one huge paragraph chances are you'll give up soon enough and look for some other source of information. One that is made for human consumption.
 +
 +=== Stack depth ===
 +Speaking of stack depth: partitioning your code into smaller functions may indeed //reduce// your stack requirement as you won't be needing to allocate every-single-variable-ever-used-in-any-branch in one chunk, but instead only use up as much stack as needed for each individual function.
 ==== 7. Code comments ==== ==== 7. Code comments ====
 +<code C>CyBool_t isUsbConnected = CyFalse; /* Whether USB connection is active. */
 +
 +int i = 1;   // set i to 1
 +
 +i++;         // increment i by 1</code>
  
 +The comments above are utterly useless. Not only they don't anything to what is already expressed in the code((which is bad enough on its own)), there's a high potential for these types of comments to become stale and ultimately very misleading.

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