diff options
Diffstat (limited to 'contrib/gcc/doc/trouble.texi')
| -rw-r--r-- | contrib/gcc/doc/trouble.texi | 169 |
1 files changed, 33 insertions, 136 deletions
diff --git a/contrib/gcc/doc/trouble.texi b/contrib/gcc/doc/trouble.texi index 4cfef9f..4a8f0c3 100644 --- a/contrib/gcc/doc/trouble.texi +++ b/contrib/gcc/doc/trouble.texi @@ -163,7 +163,7 @@ Naturally, this does not happen when you use GCC@. You must specify all three options explicitly. @item -On a Sparc, GCC aligns all values of type @code{double} on an 8-byte +On a SPARC, GCC aligns all values of type @code{double} on an 8-byte boundary, and it expects every @code{double} to be so aligned. The Sun compiler usually gives @code{double} values 8-byte alignment, with one exception: function arguments of type @code{double} may not be aligned. @@ -202,7 +202,7 @@ Storing into the pointer can be done likewise with the same union. @item On Solaris, the @code{malloc} function in the @file{libmalloc.a} library may allocate memory that is only 4 byte aligned. Since GCC on the -Sparc assumes that doubles are 8 byte aligned, this may result in a +SPARC assumes that doubles are 8 byte aligned, this may result in a fatal signal if doubles are stored in memory allocated by the @file{libmalloc.a} library. @@ -219,7 +219,7 @@ when linking, compile and link against the file @file{mit/util/misc/dlsym.c} from the MIT version of X windows. @item -The 128-bit long double format that the Sparc port supports currently +The 128-bit long double format that the SPARC port supports currently works by using the architecturally defined quad-word floating point instructions. Since there is no hardware that supports these instructions they must be emulated by the operating system. Long @@ -338,47 +338,6 @@ you cannot successfully use @samp{$} in identifiers on the RS/6000 due to a restriction in the IBM assembler. GAS supports these identifiers. -@item -@opindex mno-serialize-volatile -There is an assembler bug in versions of DG/UX prior to 5.4.2.01 that -occurs when the @samp{fldcr} instruction is used. GCC uses -@samp{fldcr} on the 88100 to serialize volatile memory references. Use -the option @option{-mno-serialize-volatile} if your version of the -assembler has this bug. - -@item -On VMS, GAS versions 1.38.1 and earlier may cause spurious warning -messages from the linker. These warning messages complain of mismatched -psect attributes. You can ignore them. - -@item -On NewsOS version 3, if you include both of the files @file{stddef.h} -and @file{sys/types.h}, you get an error because there are two typedefs -of @code{size_t}. You should change @file{sys/types.h} by adding these -lines around the definition of @code{size_t}: - -@smallexample -#ifndef _SIZE_T -#define _SIZE_T -@var{actual-typedef-here} -#endif -@end smallexample - -@cindex Alliant -@item -On the Alliant, the system's own convention for returning structures -and unions is unusual, and is not compatible with GCC no matter -what options are used. - -@cindex RT PC -@cindex IBM RT PC -@item -@opindex mhc-struct-return -On the IBM RT PC, the MetaWare HighC compiler (hc) uses a different -convention for structure and union returning. Use the option -@option{-mhc-struct-return} to tell GCC to use a convention compatible -with it. - @cindex VAX calling convention @cindex Ultrix calling convention @item @@ -395,42 +354,10 @@ these options to produce code compatible with the Fortran compiler: @end smallexample @item -On the WE32k, you may find that programs compiled with GCC do not -work with the standard shared C library. You may need to link with -the ordinary C compiler. If you do so, you must specify the following -options: - -@smallexample --L/usr/local/lib/gcc-lib/we32k-att-sysv/2.8.1 -lgcc -lc_s -@end smallexample - -The first specifies where to find the library @file{libgcc.a} -specified with the @option{-lgcc} option. - -GCC does linking by invoking @command{ld}, just as @command{cc} does, and -there is no reason why it @emph{should} matter which compilation program -you use to invoke @command{ld}. If someone tracks this problem down, -it can probably be fixed easily. - -@item On the Alpha, you may get assembler errors about invalid syntax as a result of floating point constants. This is due to a bug in the C library functions @code{ecvt}, @code{fcvt} and @code{gcvt}. Given valid floating point numbers, they sometimes print @samp{NaN}. - -@item -On Irix 4.0.5F (and perhaps in some other versions), an assembler bug -sometimes reorders instructions incorrectly when optimization is turned -on. If you think this may be happening to you, try using the GNU -assembler; GAS version 2.1 supports ECOFF on Irix. - -@opindex noasmopt -Or use the @option{-noasmopt} option when you compile GCC with itself, -and then again when you compile your program. (This is a temporary -kludge to turn off assembler optimization on Irix.) If this proves to -be what you need, edit the assembler spec in the file @file{specs} so -that it unconditionally passes @option{-O0} to the assembler, and never -passes @option{-O2} or @option{-O3}. @end itemize @node External Bugs @@ -445,8 +372,7 @@ Parse errors may occur compiling X11 on a Decstation running Ultrix 4.2 because of problems in DEC's versions of the X11 header files @file{X11/Xlib.h} and @file{X11/Xutil.h}. People recommend adding @option{-I/usr/include/mit} to use the MIT versions of the header files, -using the @option{-traditional} switch to turn off ISO C, or fixing the -header files by adding this: +or fixing the header files by adding this: @example #ifdef __STDC__ @@ -486,9 +412,7 @@ MALLOC=gmalloc.o @opindex traditional There are several noteworthy incompatibilities between GNU C and K&R -(non-ISO) versions of C@. The @option{-traditional} option -eliminates many of these incompatibilities, @emph{but not all}, by -telling GCC to behave like a K&R C compiler. +(non-ISO) versions of C@. @itemize @bullet @cindex string constants @@ -518,7 +442,6 @@ The best solution to these problems is to change the program to use purposes instead of string constants. But if this is not possible, you can use the @option{-fwritable-strings} flag, which directs GCC to handle string constants the same way most C compilers do. -@option{-traditional} also has this effect, among others. @item @code{-2147483648} is positive. @@ -538,9 +461,6 @@ string constants. For example, the following macro in GCC @noindent will produce output @code{"a"} regardless of what the argument @var{a} is. -The @option{-traditional} option directs GCC to handle such cases -(among others) in the old-fashioned (non-ISO) fashion. - @cindex @code{setjmp} incompatibilities @cindex @code{longjmp} incompatibilities @item @@ -575,11 +495,6 @@ in it. If you use the @option{-W} option with the @option{-O} option, you will get a warning when GCC thinks such a problem might be possible. -The @option{-traditional} option directs GCC to put variables in -the stack by default, rather than in registers, in functions that -call @code{setjmp}. This results in the behavior found in -traditional C compilers. - @item Programs that use preprocessing directives in the middle of macro arguments do not work with GCC@. For example, a program like this @@ -593,9 +508,7 @@ foobar ( @end group @end example -ISO C does not permit such a construct. It would make sense to support -it when @option{-traditional} is used, but it is too much work to -implement. +ISO C does not permit such a construct. @item K&R compilers allow comments to cross over an inclusion boundary @@ -613,9 +526,6 @@ have the same scope as any other declaration in the same place. In some other C compilers, a @code{extern} declaration affects all the rest of the file even if it happens within a block. -The @option{-traditional} option directs GCC to treat all @code{extern} -declarations as global, like traditional compilers. - @item In traditional C, you can combine @code{long}, etc., with a typedef name, as shown here: @@ -626,18 +536,15 @@ typedef long foo bar; @end example In ISO C, this is not allowed: @code{long} and other type modifiers -require an explicit @code{int}. Because this criterion is expressed -by Bison grammar rules rather than C code, the @option{-traditional} -flag cannot alter it. +require an explicit @code{int}. @cindex typedef names as function parameters @item -PCC allows typedef names to be used as function parameters. The -difficulty described immediately above applies here too. +PCC allows typedef names to be used as function parameters. @item -When in @option{-traditional} mode, GCC allows the following erroneous -pair of declarations to appear together in a given scope: +Traditional C allows the following erroneous pair of declarations to +appear together in a given scope: @example typedef int foo; @@ -645,19 +552,18 @@ typedef foo foo; @end example @item -GCC treats all characters of identifiers as significant, even when in -@option{-traditional} mode. According to K&R-1 (2.2), ``No more than the -first eight characters are significant, although more may be used.''. -Also according to K&R-1 (2.2), ``An identifier is a sequence of letters -and digits; the first character must be a letter. The underscore _ -counts as a letter.'', but GCC also allows dollar signs in identifiers. +GCC treats all characters of identifiers as significant. According to +K&R-1 (2.2), ``No more than the first eight characters are significant, +although more may be used.''. Also according to K&R-1 (2.2), ``An +identifier is a sequence of letters and digits; the first character must +be a letter. The underscore _ counts as a letter.'', but GCC also +allows dollar signs in identifiers. @cindex whitespace @item PCC allows whitespace in the middle of compound assignment operators such as @samp{+=}. GCC, following the ISO standard, does not -allow this. The difficulty described immediately above applies here -too. +allow this. @cindex apostrophes @cindex ' @@ -675,8 +581,7 @@ You can't expect this to work. @end example The best solution to such a problem is to put the text into an actual -C comment delimited by @samp{/*@dots{}*/}. However, -@option{-traditional} suppresses these error messages. +C comment delimited by @samp{/*@dots{}*/}. @item Many user programs contain the declaration @samp{long time ();}. In the @@ -916,27 +821,20 @@ You can partially avoid this problem by using the @option{-ffloat-store} option (@pxref{Optimize Options}). @item -On the MIPS, variable argument functions using @file{varargs.h} -cannot have a floating point value for the first argument. The -reason for this is that in the absence of a prototype in scope, -if the first argument is a floating point, it is passed in a -floating point register, rather than an integer register. - -If the code is rewritten to use the ISO standard @file{stdarg.h} -method of variable arguments, and the prototype is in scope at -the time of the call, everything will work fine. - -@item -On the H8/300 and H8/300H, variable argument functions must be -implemented using the ISO standard @file{stdarg.h} method of -variable arguments. Furthermore, calls to functions using @file{stdarg.h} -variable arguments must have a prototype for the called function -in scope at the time of the call. - -@item On AIX and other platforms without weak symbol support, templates need to be instantiated explicitly and symbols for static members of templates will not be generated. + +@item +On AIX, GCC scans object files and library archives for static +constructors and destructors when linking an application before the +linker prunes unreferenced symbols. This is necessary to prevent the +AIX linker from mistakenly assuming that static constructor or +destructor are unused and removing them before the scanning can occur. +All static constructors and destructors found will be referenced even +though the modules in which they occur may not be used by the program. +This may lead to both increased executable size and unexpected symbol +references. @end itemize @node C++ Misunderstandings @@ -988,9 +886,9 @@ int Foo::bar = 0; @end example Other C++ compilers may not correctly implement the standard behavior. -As a result, when you switch to @code{g++} from one of these compilers, +As a result, when you switch to @command{g++} from one of these compilers, you may discover that a program that appeared to work correctly in fact -does not conform to the standard: @code{g++} reports as undefined +does not conform to the standard: @command{g++} reports as undefined symbols any static data members that lack definitions. @node Temporaries @@ -1298,12 +1196,11 @@ they write programs which have the same meaning in both C dialects.) @item @opindex ansi -@opindex traditional @opindex std Undefining @code{__STDC__} when @option{-ansi} is not used. -Currently, GCC defines @code{__STDC__} as long as you don't use -@option{-traditional}. This provides good results in practice. +Currently, GCC defines @code{__STDC__} unconditionally. This provides +good results in practice. Programmers normally use conditionals on @code{__STDC__} to ask whether it is safe to use certain features of ISO C, such as function |
