printLineFromFileAnyOs
Function parameters
Parameters
- writer:*Writer
Type definitions in this namespace
Types
- SourceLocation
- Unresolved source locations can be represented with a single `usize` that
A fully-featured panic handler namespace which lowers all panics to calls to `panicFn`.
Functions
- FullPanic
- A fully-featured panic handler namespace which lowers all panics to calls to `panicFn`.
- lockStdErr
- Allows the caller to freely write to stderr until `unlockStdErr` is called.
- lockStderrWriter
- Allows the caller to freely write to stderr until `unlockStdErr` is called.
- Print to stderr, silently returning on failure.
- dumpHex
- Tries to print a hexadecimal view of the bytes, unbuffered, and ignores any error returned.
- dumpHexFallible
- Prints a hexadecimal view of the bytes, returning any error that occurs.
- dumpCurrentStackTrace
- Tries to print the current stack trace to stderr, unbuffered, and ignores any error returned.
- dumpCurrentStackTraceToWriter
- Prints the current stack trace to the provided writer.
- copyContext
- Copies one context to another, updating any internal pointers
- relocateContext
- Updates any internal pointers in the context to reflect its current location
- getContext
- Capture the current context.
- dumpStackTraceFromBase
- Tries to print the stack trace starting from the supplied base pointer to stderr,
- captureStackTrace
- Returns a slice with the same pointer as addresses, with a potentially smaller len.
- dumpStackTrace
- Tries to print a stack trace to stderr, unbuffered, and ignores any error returned.
- assert
- Invokes detectable illegal behavior when `ok` is `false`.
- assertReadable
- Invokes detectable illegal behavior when the provided slice is not mapped
- assertAligned
- Invokes detectable illegal behavior when the provided array is not aligned
- panic
- Equivalent to `@panic` but with a formatted message.
- panicExtra
- Equivalent to `@panic` but with a formatted message, and with an explicitly
- defaultPanic
- Dumps a stack trace to standard error, then aborts.
- attachSegfaultHandler
- Attaches a global SIGSEGV handler which calls `@panic("segmentation fault");`
- inValgrind
- Detect whether the program is being executed in the Valgrind virtual machine.
Deprecated because it returns the optimization mode of the standard
Values
- runtime_safety
- Deprecated because it returns the optimization mode of the standard
- sys_can_stack_trace
- = switch (builtin.cpu.arch) { // Observed to go into an infinite loop. // TODO: Make this work. .mips, .mipsel, .mips64, .mips64el, .s390x, => false, // `@returnAddress()` in LLVM 10 gives // "Non-Emscripten WebAssembly hasn't implemented __builtin_return_address". // On Emscripten, Zig only supports `@returnAddress()` in debug builds // because Emscripten's implementation is very slow. .wasm32, .wasm64, => native_os == .emscripten and builtin.mode == .Debug, // `@returnAddress()` is unsupported in LLVM 13. .bpfel, .bpfeb, => false, else => true, }
- have_ucontext
- = posix.ucontext_t != void
- ThreadContext
- Platform-specific thread state.
- have_getcontext
- = @TypeOf(posix.system.getcontext) != void
- have_segfault_handling_support
- Whether or not the current target can print useful debug information when a segfault occurs.
- default_enable_segfault_handler
- = runtime_safety and have_segfault_handling_support
Source
Implementation
fn printLineFromFileAnyOs(writer: *Writer, source_location: SourceLocation) !void {
// Need this to always block even in async I/O mode, because this could potentially
// be called from e.g. the event loop code crashing.
var f = try fs.cwd().openFile(source_location.file_name, .{});
defer f.close();
// TODO fstat and make sure that the file has the correct size
var buf: [4096]u8 = undefined;
var amt_read = try f.read(buf[0..]);
const line_start = seek: {
var current_line_start: usize = 0;
var next_line: usize = 1;
while (next_line != source_location.line) {
const slice = buf[current_line_start..amt_read];
if (mem.indexOfScalar(u8, slice, '\n')) |pos| {
next_line += 1;
if (pos == slice.len - 1) {
amt_read = try f.read(buf[0..]);
current_line_start = 0;
} else current_line_start += pos + 1;
} else if (amt_read < buf.len) {
return error.EndOfFile;
} else {
amt_read = try f.read(buf[0..]);
current_line_start = 0;
}
}
break :seek current_line_start;
};
const slice = buf[line_start..amt_read];
if (mem.indexOfScalar(u8, slice, '\n')) |pos| {
const line = slice[0 .. pos + 1];
mem.replaceScalar(u8, line, '\t', ' ');
return writer.writeAll(line);
} else { // Line is the last inside the buffer, and requires another read to find delimiter. Alternatively the file ends.
mem.replaceScalar(u8, slice, '\t', ' ');
try writer.writeAll(slice);
while (amt_read == buf.len) {
amt_read = try f.read(buf[0..]);
if (mem.indexOfScalar(u8, buf[0..amt_read], '\n')) |pos| {
const line = buf[0 .. pos + 1];
mem.replaceScalar(u8, line, '\t', ' ');
return writer.writeAll(line);
} else {
const line = buf[0..amt_read];
mem.replaceScalar(u8, line, '\t', ' ');
try writer.writeAll(line);
}
}
// Make sure printing last line of file inserts extra newline
try writer.writeByte('\n');
}
}