Difference between revisions of "Ld"

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(Add a reference to gcc linker documentation.)
m (linker alignment macro in Zephyr.)
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2024-08-05 MON
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Interesting linker script macro in one of Zephy's header files . . .
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<pre>
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"
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167
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168 #ifndef BUILD_ASSERT
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169 /* Compile-time assertion that makes the build to fail.
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170  * Common implementation swallows the message.
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171  */
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172 #define BUILD_ASSERT(EXPR, MSG...) \
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173        enum _CONCAT(__build_assert_enum, __COUNTER__) { \
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174                _CONCAT(__build_assert, __COUNTER__) = 1 / !!(EXPR) \
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175        }
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176 #endif
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177
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178 /*
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179  * This is meant to be used in conjunction with __in_section() and similar
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180  * where scattered structure instances are concatenated together by the linker
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181  * and walked by the code at run time just like a contiguous array of such
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182  * structures.
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183  *
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184  * Assemblers and linkers may insert alignment padding by default whose
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185  * size is larger than the natural alignment for those structures when
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186  * gathering various section segments together, messing up the array walk.
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187  * To prevent this, we need to provide an explicit alignment not to rely
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188  * on the default that might just work by luck.
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189  *
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190  * Alignment statements in  linker scripts are not sufficient as
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191  * the assembler may add padding by itself to each segment when switching
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192  * between sections within the same file even if it merges many such segments
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193  * into a single section in the end.
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194  */
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195 #define Z_DECL_ALIGN(type) __aligned(__alignof(type)) type
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196
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"~/projects-sandbox/workspace-for-nexus/zephyr/include/zephyr/toolchain/common.h" 214 lines --99%--
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</pre>
  
  
 
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Revision as of 18:01, 5 August 2024

GNU and LLVM linker notes.

Overview

This NN page a starting point for notes, links to external references and examples of `ld` linker scripts. As of page creation time 2024 Q1 there appear to be two major linker variants: GNU ld and LLVM linker implementation.

Introductory References

Use of 'KEEP' key word in linker scripts:

How to place C global variables at a particular address:

A reference to gcc linker documentation:


2024-08-05 MON

Interesting linker script macro in one of Zephy's header files . . . 

"
167 
168 #ifndef BUILD_ASSERT
169 /* Compile-time assertion that makes the build to fail.
170  * Common implementation swallows the message.
171  */
172 #define BUILD_ASSERT(EXPR, MSG...) \
173         enum _CONCAT(__build_assert_enum, __COUNTER__) { \
174                 _CONCAT(__build_assert, __COUNTER__) = 1 / !!(EXPR) \
175         }
176 #endif
177 
178 /*
179  * This is meant to be used in conjunction with __in_section() and similar
180  * where scattered structure instances are concatenated together by the linker
181  * and walked by the code at run time just like a contiguous array of such
182  * structures.
183  *
184  * Assemblers and linkers may insert alignment padding by default whose
185  * size is larger than the natural alignment for those structures when
186  * gathering various section segments together, messing up the array walk.
187  * To prevent this, we need to provide an explicit alignment not to rely
188  * on the default that might just work by luck.
189  *
190  * Alignment statements in  linker scripts are not sufficient as
191  * the assembler may add padding by itself to each segment when switching
192  * between sections within the same file even if it merges many such segments
193  * into a single section in the end.
194  */
195 #define Z_DECL_ALIGN(type) __aligned(__alignof(type)) type
196 

"~/projects-sandbox/workspace-for-nexus/zephyr/include/zephyr/toolchain/common.h" 214 lines --99%--


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