Reasons why adding static to all the functions in a translation unit may increase the size of the resulting object file?
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My intention is to limit the visibility of a number of symbols to the translation unit where they are defined. This commit is adding 688 bytes to the resulting firmware file. Any ideas why?
The compiler involved is a GCC 4.8.2
The target device is an ESP-8266 microcontroller.
The optimizer is set to -Os.
c++ c esp8266 arduino-esp8266
asked Nov 10 at 19:31
Frank Meerkötter
1,60511421
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up vote
4
down vote
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My intention is to limit the visibility of a number of symbols to the translation unit where they are defined. This commit is adding 688 bytes to the resulting firmware file. Any ideas why?
The compiler involved is a GCC 4.8.2
The target device is an ESP-8266 microcontroller.
The optimizer is set to -Os.
c++ c esp8266 arduino-esp8266
asked Nov 10 at 19:31
Frank Meerkötter
1,60511421
4
Interesting. Perhaps after addingstaticthe functions are now inlined by the compiler, while before they were not? A function does not have to be explicitly marked withinlineto be inlined.
– kfx
Nov 10 at 19:47
In my opinion, it is good practice to do as you are doing (make all functions not used outside their TUstatic) — you can routinely see it in the C code I post on SO, though I don't usually comment on it. So, good job on doing that. If, as seems plausible, inlining causes the growth and that is a problem for you, you may need to investigate 'optimizing for space' instead of 'optimizing for speed'. (GCC 8.2.0 documentation on Optimizing options. You'll need the equivalent for 4.8.2 — easy to deduce.)
– Jonathan Leffler
Nov 10 at 21:32
2
What optimization levels are you using? Does this happen with-Osoptimisation? Probably one function is inlined twice or more, thus you will get bigger resulting firmare. Can you check what if you mark all those functions with__attribute__((__noinline__))?
– Kamil Cuk
Nov 10 at 21:36
Try compiling with-Os?
– M.M
Nov 10 at 21:55
Updated the question with the optimization level used.
– Frank Meerkötter
Nov 11 at 5:49
|
show 2 more comments
up vote
4
down vote
favorite
up vote
4
down vote
favorite
My intention is to limit the visibility of a number of symbols to the translation unit where they are defined. This commit is adding 688 bytes to the resulting firmware file. Any ideas why?
The compiler involved is a GCC 4.8.2
The target device is an ESP-8266 microcontroller.
The optimizer is set to -Os.
c++ c esp8266 arduino-esp8266
asked Nov 10 at 19:31
Frank Meerkötter
1,60511421
My intention is to limit the visibility of a number of symbols to the translation unit where they are defined. This commit is adding 688 bytes to the resulting firmware file. Any ideas why?
The compiler involved is a GCC 4.8.2
The target device is an ESP-8266 microcontroller.
The optimizer is set to -Os.
c++ c esp8266 arduino-esp8266
c++ c esp8266 arduino-esp8266
asked Nov 10 at 19:31
Frank Meerkötter
1,60511421
asked Nov 10 at 19:31
Frank Meerkötter
1,60511421
edited Nov 11 at 5:48
asked Nov 10 at 19:31
Frank Meerkötter
1,60511421
asked Nov 10 at 19:31
Frank Meerkötter
1,60511421
asked Nov 10 at 19:31
Frank Meerkötter
1,60511421
1,60511421
4
Interesting. Perhaps after addingstaticthe functions are now inlined by the compiler, while before they were not? A function does not have to be explicitly marked withinlineto be inlined.
– kfx
Nov 10 at 19:47
In my opinion, it is good practice to do as you are doing (make all functions not used outside their TUstatic) — you can routinely see it in the C code I post on SO, though I don't usually comment on it. So, good job on doing that. If, as seems plausible, inlining causes the growth and that is a problem for you, you may need to investigate 'optimizing for space' instead of 'optimizing for speed'. (GCC 8.2.0 documentation on Optimizing options. You'll need the equivalent for 4.8.2 — easy to deduce.)
– Jonathan Leffler
Nov 10 at 21:32
2
What optimization levels are you using? Does this happen with-Osoptimisation? Probably one function is inlined twice or more, thus you will get bigger resulting firmare. Can you check what if you mark all those functions with__attribute__((__noinline__))?
– Kamil Cuk
Nov 10 at 21:36
Try compiling with-Os?
– M.M
Nov 10 at 21:55
Updated the question with the optimization level used.
– Frank Meerkötter
Nov 11 at 5:49
|
show 2 more comments
4
Interesting. Perhaps after addingstaticthe functions are now inlined by the compiler, while before they were not? A function does not have to be explicitly marked withinlineto be inlined.
– kfx
Nov 10 at 19:47
In my opinion, it is good practice to do as you are doing (make all functions not used outside their TUstatic) — you can routinely see it in the C code I post on SO, though I don't usually comment on it. So, good job on doing that. If, as seems plausible, inlining causes the growth and that is a problem for you, you may need to investigate 'optimizing for space' instead of 'optimizing for speed'. (GCC 8.2.0 documentation on Optimizing options. You'll need the equivalent for 4.8.2 — easy to deduce.)
– Jonathan Leffler
Nov 10 at 21:32
2
What optimization levels are you using? Does this happen with-Osoptimisation? Probably one function is inlined twice or more, thus you will get bigger resulting firmare. Can you check what if you mark all those functions with__attribute__((__noinline__))?
– Kamil Cuk
Nov 10 at 21:36
Try compiling with-Os?
– M.M
Nov 10 at 21:55
Updated the question with the optimization level used.
– Frank Meerkötter
Nov 11 at 5:49
4
4
Interesting. Perhaps after adding
static the functions are now inlined by the compiler, while before they were not? A function does not have to be explicitly marked with inline to be inlined.– kfx
Nov 10 at 19:47
Interesting. Perhaps after adding
static the functions are now inlined by the compiler, while before they were not? A function does not have to be explicitly marked with inline to be inlined.– kfx
Nov 10 at 19:47
In my opinion, it is good practice to do as you are doing (make all functions not used outside their TU
static) — you can routinely see it in the C code I post on SO, though I don't usually comment on it. So, good job on doing that. If, as seems plausible, inlining causes the growth and that is a problem for you, you may need to investigate 'optimizing for space' instead of 'optimizing for speed'. (GCC 8.2.0 documentation on Optimizing options. You'll need the equivalent for 4.8.2 — easy to deduce.)– Jonathan Leffler
Nov 10 at 21:32
In my opinion, it is good practice to do as you are doing (make all functions not used outside their TU
static) — you can routinely see it in the C code I post on SO, though I don't usually comment on it. So, good job on doing that. If, as seems plausible, inlining causes the growth and that is a problem for you, you may need to investigate 'optimizing for space' instead of 'optimizing for speed'. (GCC 8.2.0 documentation on Optimizing options. You'll need the equivalent for 4.8.2 — easy to deduce.)– Jonathan Leffler
Nov 10 at 21:32
2
2
What optimization levels are you using? Does this happen with
-Os optimisation? Probably one function is inlined twice or more, thus you will get bigger resulting firmare. Can you check what if you mark all those functions with __attribute__((__noinline__))?– Kamil Cuk
Nov 10 at 21:36
What optimization levels are you using? Does this happen with
-Os optimisation? Probably one function is inlined twice or more, thus you will get bigger resulting firmare. Can you check what if you mark all those functions with __attribute__((__noinline__))?– Kamil Cuk
Nov 10 at 21:36
Try compiling with
-Os ?– M.M
Nov 10 at 21:55
Try compiling with
-Os ?– M.M
Nov 10 at 21:55
Updated the question with the optimization level used.
– Frank Meerkötter
Nov 11 at 5:49
Updated the question with the optimization level used.
– Frank Meerkötter
Nov 11 at 5:49
|
show 2 more comments
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4
Interesting. Perhaps after adding
staticthe functions are now inlined by the compiler, while before they were not? A function does not have to be explicitly marked withinlineto be inlined.– kfx
Nov 10 at 19:47
In my opinion, it is good practice to do as you are doing (make all functions not used outside their TU
static) — you can routinely see it in the C code I post on SO, though I don't usually comment on it. So, good job on doing that. If, as seems plausible, inlining causes the growth and that is a problem for you, you may need to investigate 'optimizing for space' instead of 'optimizing for speed'. (GCC 8.2.0 documentation on Optimizing options. You'll need the equivalent for 4.8.2 — easy to deduce.)– Jonathan Leffler
Nov 10 at 21:32
2
What optimization levels are you using? Does this happen with
-Osoptimisation? Probably one function is inlined twice or more, thus you will get bigger resulting firmare. Can you check what if you mark all those functions with__attribute__((__noinline__))?– Kamil Cuk
Nov 10 at 21:36
Try compiling with
-Os?– M.M
Nov 10 at 21:55
Updated the question with the optimization level used.
– Frank Meerkötter
Nov 11 at 5:49