DJGPP Knowledge Base: Changes in 2.03

localtime, ctime and mktime now notice changes in the value of the TZ environment variable during the program run, and adjust their computation accordingly. They also don’t fail for the first date after the epoch. mktime now avoids looping for preposterously long time when passed very large values in the members of struct tm.

When passed an empty string as the file name, stat now fails and sets errno to ENOENT, instead of returning information about the current directory. Also, stat no longer reports invalid time stamps for root directories of floppy disks that were written on Windows 9X or Windows NT.

The startup code now correctly sets up the keys that generate SIGINT and SIGQUIT signals on PC98 machines.

putc and fputc no longer return -1 when they write the value (signed char)0xff to a file.

The header wctype.h from v2.02 caused pre-processor errors, and could not be included before ctype.h. This is now fixed.

Functions of the printf family no longer cause the calling program to crash when passed long double variables with invalid bit patterns (the so-called unnormal numbers). Such arguments are now printed as ‘Unnormal’.

The rmcb stub doesn’t restore the flags so that you can return different ones.

The “Hidden Features” chapter of the Knowledge Base now actually describes most of the special features provided by DJGPP.

redir no longer fails to run programs when the program name is a substring of the redirected I/O file(s).

glob correctly converts the letter-case of the file names when the pattern include mixed upper- and lower-case letters. In particular, the letter-case of the command-line arguments expanded by the startup code in the argv[] array is now correct in these cases.

textcolor and textbackground now support the 16 background colors mode (e.g., after a call to intensevideo). Previously, textbackground would ignore the high intensity color bit in its argument, and textcolor would clobber that bit sometimes.

The global variable ScreenAttrib now always matches the value of the attribute member of the text_info struct returned by gettexinfo.

If the last character of a response file is ‘^Z’, it is now ignored. Previous versions would pass it to the main function. Use two ‘^Z’ characters in a row if you actually need to pass such a character as part of the last element of the argv[] array.

fputs now returns EOF when called on an unbuffered stream, and there’s some error (such as ENOSPC) in writing to that stream.

If both arguments of _rename and rename refer to the same file, they no longer remove that file.

Functions of the scanf family no longer crash or work incorrectly when passed format specifiers with upper-case letters, such as ‘%lX’ or ‘%E’. Non-ANSI extensions to the format specifiers and qualifiers, such as ‘%lld’ and ‘%U’, are now documented and their portability information included in the library docs.

The function __crt0_load_environment_file called by the startup code now strips trailing blanks and TABs from the ‘[program]’ lines of the DJGPP.ENV file which define sections for individual programs. This is so editing DJGPP.ENV with some losing editors that don’t strip trailing whitespace when saving the file doesn’t prevent the startup code from recognizing section names.

dtou and utod no longer overwrite the stack when invoked on file names longer than 80 characters.

system works when its argument uses redirection to/from quoted file names (e.g., when the file name includes embedded whitespace).

Buffered stdio functions, such as getc, putc, fread, printf, and all their relatives pay attention to termios settings of the terminal device and behave accordingly. For example, you can get single-character, no-echo input with the following snippet:

 struct termios charmode;

 tcgetattr (0, &charmode);
 charmode.c_lflag &= ~(ECHO | ICANON | ISIG);
 tcsetattr (0, &charmode);

If you reset the ISIG or BRKINT flags in the termios structure, or set the IGNBRK flag, tcsetattr now disables SIGINT generation by a Ctrl-C or Ctrl-BREAK keypress, and generation of SIGQUIT by pressing Ctrl-\.

A call like ‘tcflush (0, TCIFLUSH);’ now empties the BIOS keyboard buffer in addition to the internal buffer maintained by the termios input processing. This is compatible with the Unix specification that tcflush should “discard all data received but not read”.

Library function system no longer crashes when given invalid command lines which involve pipe symbols ‘|’. Typically, such command lines should have been run by a Unix-style shell, like Bash. However, sometimes, due to some system configuration snafu, the SHELL variable in the environment didn’t point to such a shell, and system would try to execute the command line using its internal emulator of COMMAND.COM; it would then crash due to a bug. This is now solved: system prints appropriate error message(s) and exits with an error code of -1. We believe that some of the rarely-reported and hard-to-reproduce crashes of the Make utility were due to this bug.

Previously, when attempt was made to open a file, and all the available file handles were exhausted, open would sometimes truncate an existing file on Windows 9X. This is now fixed.

All DJGPP programs now clear the FPU exceptions when they exit. This prevents the next DJGPP program that is run in the same DOS box on Windows 9X from crashing during startup code.

When the 387 environment variable overrides the FPU auto-detect code, the value of the global variable _8087 is now set by the startup code according to the environment override: 3 if 387 is set to ‘y’, 0 otherwise.

You can use the special /dev/env/foo/ construct in file names to expand it into the value of the environment variable foo at run time. /dev/env/foo~bar~ will expand to bar if foo is undefined, or if its value is empty.

Calling getch and getche flushes the stdout and stderr streams, if they are connected to the console and have any pending buffered characters.

A bug in the library caused programs like Emacs, which dump their data and then restart, to use stale FILE objects created before they were dumped. This caused warning messages to be issued by GDB near the end of debugging session. This bug is now fixed.

Due to a peculiarity of the timer device virtualization, the values returned by uclock on Windows during the first 54.9msec after the first call (which reprograms the timer chip) were erratic, some of them negative, some positive. To work around this, the first call to uclock on Windows now waits until the next timer tick before returning, to ensure that all the values returned hence are monotonously increasing.

The termios emulation now uses raw input/output only if the file handle referring to a device is put into binary mode, and the device itself is in raw mode.

The termios input routines no longer generate the SIGINT and SIGQUIT signals twice when Ctrl-C or Ctrl-\ are pressed.

A call to __djgpp_set_ctrl_c with a negative argument returns the current state of SIGINT and SIGQUIT generation without altering it.

The termios cooked-mode output now expands TABs into the appropriate number of spaces when writing to the console device.

The setmode function now switches character devices to raw/cooked mode even when termios functions are used.

freopen now correctly sets the read/write access flags when ‘+’ is the last (third) character of the mode string, like in ‘wt+’ or ‘ab+’.

Previously, searchpath would always return its argument unchanged and signal a success, when the argument included slashes or a drive letter, even if the file didn’t actually exist. This is now fixed: non-existent files always cause searchpath to return a NULL pointer.

The DJGPP debug support functions in libdbg.a now have the capability to debug programs that catch signals such as SIGINT. The signal interrupts the debuggee and is reported by the debugger, instead of aborting the debuggee. You can also deliver signals to the debuggee, even if they didn’t actually happen. Most of the work that made this possible was done by Pierre Muller and Andris Pavenis.

The debugging support functions in libdbg.a now correctly handle the SIGQUIT signal that happens while the debuggee runs. Previously, a debugger would crash or report SIGINT in such cases.

The DJGPP functions in libdbg.a support FP code much better now, especially when FP exceptions happen in the debugged program. The full state of the numeric processor is saved and restored when the execution thread jumps from the debugger to the debuggee and back.

It is now possible to debug programs that redirect their standard handles, without the debugger losing those handles at the same time. Debuggers which want to use this feature need to call the new redir_* functions before and after jumping to the debuggee’s code. See Redirection in the debugger in libc.a reference.

The documentation for the debug support functions in libdbg.a is now part of the library reference.

When a raw COFF image (i.e., without a stub) is debugged, its stack length and the size of transfer buffer are now taken from the values used by the debugger. This means that you can have predictable results by stubediting the debugger’s executable.

__dpmi_simulate_real_mode_procedure_retf_stack no longer fills part of the real-mode stack with garbage. The parameters specification was changed so that the second argument is now the number of 16-bit words to copy to the real-mode stack, like the DPMI spec requires.

The floating-point emulator software had a bug in emulation of subtraction, addition, and comparison instructions, whereby the results produced for some rare pairs of numbers with the same exponent but different mantissa were grossly incorrect. This is now fixed. This bug was known to cause all kinds of weird failures, like incorrect values produced by functions sin and cos, programs being trapped inside infinite loops when they called acos, etc.

The FP emulation library libemu.a omitted the specially-compiled FPU setup module npxsetup.o which arranges for floating-point instructions to call functions from libemu.a. This caused programs linked with ‘-lemu’ to require the dynamically-loaded emulator, emu387.dxe, even though the emulation code was linked into the program. This bug is now fixed.

rename now sets errno to EACCES when an attempt is made to rename an open file. Previously, errno was set to ENOENT in these cases.

Library functions that process strings and file names, such as strupr, stricmp, strtol, fnmatch, and the functions from printf and scanf families, handle 8-bit characters correctly when they call ctype character-classification functions internally.

New versions of mathematical functions, written by Eric Rudd, are now included in the standard C library, libc.a. The new versions are ANSI-compatible (they set errno in case of FP errors), yet very fast and accurate. Programs that require accurate floating-point computations can now be linked without ‘-lm’, unless they need the matherr call-back or compliance to standards like X/Open or SVID.

New math functions are provided: powi, cbrt, expm1, exp2, exp10, and sincos.

If the format specifier for a floating-point number includes the ‘+’ flag (meaning that the sign should be printed even if the number is positive), the functions of the printf family will now print the negative zero, -0.0, with an explicit negative sign.

access no longer loses a FileFind handle on LFN platforms when called on a root directory or a character device.

_check_v2_prog no longer leaks file descriptors when called on a corrupt executable by name.

setitimer no longer crashes when its second argument is a NULL pointer, it simply returns after setting the third argument to the value of the last timer set with a previous call to setitimer.

setitimer now rounds up timer values smaller than the system clock granularity to that granularity, before it uses the values. Therefore, setitimer and getitimer will return rounded up values for such small timers. The global variable __djgpp_clock_tick_interval is provided for changing the granularity used by setitimer, in case an application reprograms the timer chip to run with a non-standard frequency.

ftruncate now leaves the file pointer at the same byte position as it were before the function was called.

Functions of the scanf family now correctly stop the scan when they encounter a digit larger than 7, and either the format specifies octal conversion, like in %o, or the format is %i and the leading digit is 0, which implies octal conversion.

Functions of the scanf family now use 16 as the base for converting pointer values read with the %p format. Thus, reading back a pointer written with the %p format now yields the original value.

kill now sets errno to ENOSYS when called with a pid argument that isn’t the caller’s PID, since DOS doesn’t allow sending signals to other processes.

The startup code and the linker script file djgpp.djl include support for long section names. Long section names are required by the latest versions of GNU Binutils to support automatic template instantiation in C++ programs.

realloc no longer crashes when the available virtual memory is not enough to satisfy the reallocation request.

Previously, the symlink function would sometimes think that the source and the target of the link were in the same directory, when in fact they weren’t. This bug is now fixed.

djtar now creates the file tarchange.lst only if it actually needs to rename some of the files during unpacking. In particular, simply listing the contents of an archive, as in ‘djtar foo.tgz’, will not produce an empty tarchange.lst file anymore.

The function memicmp was omitted from the library in version 2.02. This is fixed now.

Previously, fsdb could not step over function calls when 4 or more breakpoints were set: it would display an error message saying that ‘Exception 3 occurred’. This is now fixed. In addition, fsdb now supports the SIGQUIT signal, if the program being debugged generates it.

The floating-point emulation now works on Windows. Previously, a bug in the emulation of the WAIT/FWAIT instructions caused the emulator to get stuck in an endless loop on Windows. (On MS-DOS, these two instructions don’t generate an FP exception, and so don’t get into the emulator.)

The emulator setup in the startup code now correctly masks all FP exceptions in the emulated control word, like the hardware FPU setup does. If some numeric exception is unmasked by an application and is triggered by some abnormal condition in the emulator (e.g., if an application attempts to compute a square root of a negative number), the emulation simulates exception 16, the Coprocessor Error exception. (Previously, the exception number in the DJGPP exception structure was not set by the emulation, and was left at its old value set by the Coprocessor Not Present exception generated by the emulated instruction. This caused incorrect message to be printed when the program crashed, and defeated user-defined handlers for SIGFPE.)

The emulator now correctly sets the condition code bits C0, C1, C2, and C3 when an exceptional condition is raised, and as result of emulating the FPREM and FPREM1 instructions.

The floating-point emulator software had a bug in emulation of the FSQRT instruction, which could cause the calling program to hang. This was due to incorrect optimization by the version of GCC used to produce djdev202.zip. The new version of the emulator works around this bug by preventing the compiler from performing these incorrect optimizations.

fsetpos no longer returns zero when it fails to move the file position pointer.

djtar now converts .info- into .i only if the character following .info- is a digit. .tar.gz is converted to .tgz only at the end of a file name. ++ is converted to xx (instead of plus in previous versions), and this conversion is performed for all occurrences of ++ in a file name (previous versions only converted the first occurrence).

The gxx compiler driver no longer reports an error if the optional GNU C++ class library libgpp.a is not installed. If libgpp.a cannot be found where gcc would look for it, gxx does not pass the ‘-lgpp’ option to the linker. Also, if the standard C++ library, libstdcxx.a, cannot be found, gxx now tries libstdcx.a and libstd~1.a, in case the user has some LFN-related installation snafu.

The FP emulation behaves closer to a real FPU when an FP instruction produces abnormal results, such as Inf or NaN. In particular:

The wchar_t data type is changed so that DJGPP now supports 16-bit wide characters. This is required for RSXNTDJ programs to be compatible with Windows implementation of Unicode.

The long file-name (LFN) support is no longer disabled after _use_lfn (or some other library functions that call it) were called with a file name which refers to an invalid drive or a drive whose media has been removed (e.g. an empty floppy drive). _get_volume_info now returns _FILESYS_UNKNOWN for such drives.

symify no longer crashes when the name of the function or source file are too long to fit on a single screen line. It also doesn’t overwrite the address on the next screen line. Instead, symify truncates the long names to fit on a single screen line.

tmpfile no longer gets stuck in an endless loop when all the available file handles are exhausted.

2.3 Changes in 2.03