链接器文件中输入段与输出段的差异是什么？

Great question—this is one of those terminology nuances that trips up a lot of people when digging into ELF internals, even once you’ve got a handle on what a "segment" broadly is. Let’s break down the key differences clearly:

Input Segments #

• Where they come from: Input segments are the raw, per-object-file segments generated by your compiler/assembler when you compile individual source files. For example, when you compile foo.c into foo.o, that .o file will have its own .text (code), .data (initialized data), and .bss (uninitialized data) segments—these are all input segments.
• Core role: They’re the building blocks the linker works with. Each input segment carries specific attributes (like whether it’s executable, read-only, or writable) and contains the code/data from a single translation unit.
• Key trait: They’re isolated to individual target files. If you have 5 .o files, you’ve got 5 separate .text input segments, each holding code from one source file.

Output Segments #

• Where they come from: Output segments are the finished, consolidated segments in your final executable, shared library, or object file produced by the linker. The linker takes all matching input segments (e.g., all .text segments from every .o file) and merges, relocates, and organizes them into a single output segment.
• Core role: They’re what the OS loader uses to map your program into memory. Each output segment defines a contiguous block of memory with consistent permissions—for example, the final .text output segment is a single read-executable block containing all your program’s code, ready to run.
• Key trait: They represent the final memory layout of your program. Linkers also let you customize output segments via scripts (like ld scripts), letting you group input segments in non-default ways if needed.

Quick Summary #

Think of input segments as the individual pieces of a puzzle, and output segments as the fully assembled puzzle sections that fit together to make the whole program. The distinction matters because it clarifies the linker’s workflow: it takes scattered input segments, processes them, and packages them into cohesive output segments that the system can execute.

内容的提问来源于stack exchange，提问作者urnenfeld