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Source file src/cmd/compile/doc.go

Documentation: cmd/compile

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  /*
     6  Compile, typically invoked as ``go tool compile,'' compiles a single Go package
     7  comprising the files named on the command line. It then writes a single
     8  object file named for the basename of the first source file with a .o suffix.
     9  The object file can then be combined with other objects into a package archive
    10  or passed directly to the linker (``go tool link''). If invoked with -pack, the compiler
    11  writes an archive directly, bypassing the intermediate object file.
    12  
    13  The generated files contain type information about the symbols exported by
    14  the package and about types used by symbols imported by the package from
    15  other packages. It is therefore not necessary when compiling client C of
    16  package P to read the files of P's dependencies, only the compiled output of P.
    17  
    18  Command Line
    19  
    20  Usage:
    21  
    22  	go tool compile [flags] file...
    23  
    24  The specified files must be Go source files and all part of the same package.
    25  The same compiler is used for all target operating systems and architectures.
    26  The GOOS and GOARCH environment variables set the desired target.
    27  
    28  Flags:
    29  
    30  	-D path
    31  		Set relative path for local imports.
    32  	-I dir1 -I dir2
    33  		Search for imported packages in dir1, dir2, etc,
    34  		after consulting $GOROOT/pkg/$GOOS_$GOARCH.
    35  	-L
    36  		Show complete file path in error messages.
    37  	-N
    38  		Disable optimizations.
    39  	-S
    40  		Print assembly listing to standard output (code only).
    41  	-S -S
    42  		Print assembly listing to standard output (code and data).
    43  	-V
    44  		Print compiler version and exit.
    45  	-asmhdr file
    46  		Write assembly header to file.
    47  	-blockprofile file
    48  		Write block profile for the compilation to file.
    49  	-complete
    50  		Assume package has no non-Go components.
    51  	-cpuprofile file
    52  		Write a CPU profile for the compilation to file.
    53  	-dynlink
    54  		Allow references to Go symbols in shared libraries (experimental).
    55  	-e
    56  		Remove the limit on the number of errors reported (default limit is 10).
    57  	-h
    58  		Halt with a stack trace at the first error detected.
    59  	-importmap old=new
    60  		Interpret import "old" as import "new" during compilation.
    61  		The option may be repeated to add multiple mappings.
    62  	-installsuffix suffix
    63  		Look for packages in $GOROOT/pkg/$GOOS_$GOARCH_suffix
    64  		instead of $GOROOT/pkg/$GOOS_$GOARCH.
    65  	-l
    66  		Disable inlining.
    67  	-largemodel
    68  		Generate code that assumes a large memory model.
    69  	-linkobj file
    70  		Write linker-specific object to file and compiler-specific
    71  		object to usual output file (as specified by -o).
    72  		Without this flag, the -o output is a combination of both
    73  		linker and compiler input.
    74  	-memprofile file
    75  		Write memory profile for the compilation to file.
    76  	-memprofilerate rate
    77  		Set runtime.MemProfileRate for the compilation to rate.
    78  	-msan
    79  		Insert calls to C/C++ memory sanitizer.
    80  	-mutexprofile file
    81  		Write mutex profile for the compilation to file.
    82  	-nolocalimports
    83  		Disallow local (relative) imports.
    84  	-o file
    85  		Write object to file (default file.o or, with -pack, file.a).
    86  	-p path
    87  		Set expected package import path for the code being compiled,
    88  		and diagnose imports that would cause a circular dependency.
    89  	-pack
    90  		Write a package (archive) file rather than an object file
    91  	-race
    92  		Compile with race detector enabled.
    93  	-trimpath prefix
    94  		Remove prefix from recorded source file paths.
    95  	-u
    96  		Disallow importing packages not marked as safe; implies -nolocalimports.
    97  
    98  There are also a number of debugging flags; run the command with no arguments
    99  for a usage message.
   100  
   101  Compiler Directives
   102  
   103  The compiler accepts compiler directives in the form of // comments at the
   104  beginning of a line. To distinguish them from non-directive comments, the directives
   105  require no space between the slashes and the name of the directive. However, since
   106  they are comments, tools unaware of the directive convention or of a particular
   107  directive can skip over a directive like any other comment.
   108  
   109  	//line path/to/file:linenumber
   110  
   111  The //line directive specifies that the source line that follows should be recorded
   112  as having come from the given file path and line number. Successive lines are
   113  recorded using increasing line numbers, until the next directive. This directive
   114  typically appears in machine-generated code, so that compilers and debuggers
   115  will show lines in the original input to the generator.
   116  
   117  The //line directive is an historical special case; all other directives are of the form
   118  //go:name, indicating that the directive is defined by the Go toolchain.
   119  
   120  	//go:noescape
   121  
   122  The //go:noescape directive specifies that the next declaration in the file, which
   123  must be a func without a body (meaning that it has an implementation not written
   124  in Go) does not allow any of the pointers passed as arguments to escape into the
   125  heap or into the values returned from the function. This information can be used
   126  during the compiler's escape analysis of Go code calling the function.
   127  
   128  	//go:nosplit
   129  
   130  The //go:nosplit directive specifies that the next function declared in the file must
   131  not include a stack overflow check. This is most commonly used by low-level
   132  runtime sources invoked at times when it is unsafe for the calling goroutine to be
   133  preempted.
   134  
   135  	//go:linkname localname importpath.name
   136  
   137  The //go:linkname directive instructs the compiler to use ``importpath.name'' as the
   138  object file symbol name for the variable or function declared as ``localname'' in the
   139  source code. Because this directive can subvert the type system and package
   140  modularity, it is only enabled in files that have imported "unsafe".
   141  */
   142  package main
   143  

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