tests: improve diagnostic output on failure

vlib/builtin/builtin.v

@@ -32,26 +32,31 @@ pub fn print_backtrace() {
 
 // replaces panic when -debug arg is passed
 fn panic_debug(line_no int, file, mod, fn_name, s string) {
-	println('================ V panic ================')
-	println('   module: $mod')
-	println(' function: ${fn_name}()')
-	println('     file: $file')
-	println('     line: ' + line_no.str())
-	println('  message: $s')
-	println('=========================================')
+	// NB: the order here is important for a stabler test output
+	// module is less likely to change than function, etc...
+	// During edits, the line number will change most frequently,
+	// so it is last
+	eprintln('================ V panic ================')
+	eprintln('   module: $mod')
+	eprintln(' function: ${fn_name}()')
+	eprintln('  message: $s')
+	eprintln('     file: $file')
+	eprintln('     line: ' + line_no.str())
+	eprintln('=========================================')
 	print_backtrace_skipping_top_frames(1)
 	C.exit(1)
 }
 
 pub fn panic(s string) {
-	println('V panic: $s')
+	eprintln('V panic: $s')
 	print_backtrace()
 	C.exit(1)
 }
 
 pub fn eprintln(s string) {
+	// eprintln is used in panics, so it should not fail at all
 	if s.str == 0 {
-		panic('eprintln(NIL)')
+		eprintln('eprintln(NIL)')
 	}
 	$if !windows {
 		C.fflush(C.stdout)
@@ -66,7 +71,7 @@ pub fn eprintln(s string) {
 
 pub fn eprint(s string) {
 	if s.str == 0 {
-		panic('eprint(NIL)')
+		eprintln('eprint(NIL)')
 	}
 	$if !windows {
 		C.fflush(C.stdout)

vlib/builtin/builtin_nix.c.v

@@ -65,7 +65,7 @@ fn print_backtrace_skipping_top_frames_mac(skipframes int) bool {
 	$if macos {
 		buffer := [100]byteptr
 		nr_ptrs := backtrace(buffer, 100)
-		backtrace_symbols_fd(&buffer[skipframes], nr_ptrs - skipframes, 1)
+		backtrace_symbols_fd(&buffer[skipframes], nr_ptrs - skipframes, 2)
 	}
 	return true
 }
@@ -74,7 +74,7 @@ fn print_backtrace_skipping_top_frames_freebsd(skipframes int) bool {
 	$if freebsd {
 		buffer := [100]byteptr
 		nr_ptrs := backtrace(buffer, 100)
-		backtrace_symbols_fd(&buffer[skipframes], nr_ptrs - skipframes, 1)
+		backtrace_symbols_fd(&buffer[skipframes], nr_ptrs - skipframes, 2)
 	}
 	return true
 }
@@ -104,7 +104,7 @@ fn print_backtrace_skipping_top_frames_linux(skipframes int) bool {
 				// taken from os, to avoid depending on the os module inside builtin.v
 				f := C.popen(cmd.str, 'r')
 				if isnil(f) {
-					println(sframe)
+					eprintln(sframe)
 					continue
 				}
 				buf := [1000]byte
@@ -114,7 +114,7 @@ fn print_backtrace_skipping_top_frames_linux(skipframes int) bool {
 				}
 				output = output.trim_space() + ':'
 				if C.pclose(f) != 0 {
-					println(sframe)
+					eprintln(sframe)
 					continue
 				}
 				if output in ['??:0:', '??:?:'] {
@@ -124,13 +124,13 @@ fn print_backtrace_skipping_top_frames_linux(skipframes int) bool {
 				// NB: it is shortened here to just d. , just so that it fits, and so
 				// that the common error file:lineno: line format is enforced.
 				output = output.replace(' (discriminator', ': (d.')
-				println('${output:-46s} | ${addr:14s} | $beforeaddr')
+				eprintln('${output:-46s} | ${addr:14s} | $beforeaddr')
 			}
 			// backtrace_symbols_fd(*voidptr(&buffer[skipframes]), nr_actual_frames, 1)
 			return true
 		} $else {
-			println('backtrace_symbols_fd is missing, so printing backtraces is not available.\n')
-			println('Some libc implementations like musl simply do not provide it.')
+			eprintln('backtrace_symbols_fd is missing, so printing backtraces is not available.\n')
+			eprintln('Some libc implementations like musl simply do not provide it.')
 		}
 	}
 	return false

vlib/builtin/builtin_windows.c.v

@@ -69,12 +69,11 @@ fn builtin_init() {
 fn print_backtrace_skipping_top_frames(skipframes int) bool {
 	$if msvc {
 		return print_backtrace_skipping_top_frames_msvc(skipframes)
-
 	}
 	$if mingw {
 		return print_backtrace_skipping_top_frames_mingw(skipframes)
 	}
-	println('print_backtrace_skipping_top_frames is not implemented')
+	eprintln('print_backtrace_skipping_top_frames is not implemented')
 	return false
 }
 
@@ -97,7 +96,7 @@ $if msvc {
 
 	syminitok := C.SymInitialize( handle, 0, 1)
 	if syminitok != 1 {
-		println('Failed getting process: Aborting backtrace.\n')
+		eprintln('Failed getting process: Aborting backtrace.\n')
 		return true
 	}
 
@@ -115,27 +114,29 @@ $if msvc {
 				lineinfo = '?? : address = 0x${&frame_addr:x}'
 			}
 			sfunc := tos3(fname)
-			println('${nframe:-2d}: ${sfunc:-25s}  $lineinfo')
+			eprintln('${nframe:-2d}: ${sfunc:-25s}  $lineinfo')
 		} else {
 			// https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes
 			cerr := int(C.GetLastError())
 			if cerr == 87 {
-				println('SymFromAddr failure: $cerr = The parameter is incorrect)')
+				eprintln('SymFromAddr failure: $cerr = The parameter is incorrect)')
 			} else if cerr == 487 {
 				// probably caused because the .pdb isn't in the executable folder
-				println('SymFromAddr failure: $cerr = Attempt to access invalid address (Verify that you have the .pdb file in the right folder.)')
+				eprintln('SymFromAddr failure: $cerr = Attempt to access invalid address (Verify that you have the .pdb file in the right folder.)')
 			} else {
-				println('SymFromAddr failure: $cerr (see https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes)')
+				eprintln('SymFromAddr failure: $cerr (see https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes)')
 			}
 		}
 	}
 	return true
 } $else {
+	eprintln('print_backtrace_skipping_top_frames_msvc must be called only when the compiler is msvc')
 	return false
 }
 }
 
 fn print_backtrace_skipping_top_frames_mingw(skipframes int) bool {
+	eprintln('print_backtrace_skipping_top_frames_mingw is not implemented')
 	return false
 }
 

vlib/builtin/js/builtin.v

@@ -14,7 +14,7 @@ pub fn isnil(v voidptr) bool {
 }
 
 pub fn panic(s string) {
-	println('V panic: ' + s)
+	eprintln('V panic: ' + s)
 	exit(1)
 }