c语言的翻译叫什么,C语言中的翻译单位到底是什么

The commonly used definition of a translation unit is what comes after preprocessing (header files inclusions, macros, etc along with the source file). This definition is reasonably clear and the C standard, 5.1.1.1, C11, says:

A C program need not all be translated at the same time. The text of the program is kept in units called source files, (or preprocessing files) in this International Standard. A source file together with all the headers and source files included via the preprocessing directive #include is known as a preprocessing translation unit. After preprocessing, a preprocessing translation unit is called a translation unit.

Reading the first sentence more closely:

A C program need not all be translated at the same time.

which implies (to my reading), a C program can be translated at the same without necessarily splitting them into multiple preprocessing source files.

Also at the end of the same paragraph, the standard says:

Translation units may be separately translated and then later linked to produce an executable program.

which can be (and typically is) interpreted as compiling individual object files and then finally linking them to produce a single executable program. However, if one can make a question out of the above statement and ask: does it mean an implementation is free to consider multiple source files as a single translation unit, especially for an invocation like:

gcc file1.c file2.c -o out

where the compiler has access to the entire source?

In particular, if an implementation treats file1.c + file2.c (above) as a single translation unit, can it be considered non-conforming?

解决方案

In the second line you quoted:

The text of the program is kept in units called source files, (or preprocessing files) in this International Standard

If there are two source files then there are two preprocessing files, and therefore two preprocessing translation units, and therefore two translation units. One corresponding to each source file.

The standard doesn't define source file. I guess the compiler could say "I'm making up my own version of 'source file' by declaring that file1.c and file2.c are not source files after all!" and concatenate them, but this would be at odds with programmer expectations. I think you would have a hard time arguing that file1.c is not a source file.