mirror of
https://github.com/mirror/tinycc.git
synced 2026-08-18 11:03:27 +08:00
bcheck: remove static (compile-time) control
Providing both run-time and compile-time control for bounds checking as an user interface appears unnecessary and confusing. Also: - replace 'bound_...' by 'bounds_...' for consistency - tcc-doc: put related info into one place and cleanup The __bounds_checking(x) function is still missing explanation. (I.e. what happens if the accumulated value drops below zero.)
This commit is contained in:
grischka
104
tcc-doc.texi
104
tcc-doc.texi
@@ -351,26 +351,8 @@ invalid pointer} instead of the laconic @code{Segmentation
|
||||
fault}.
|
||||
|
||||
@item -b
|
||||
Generate additional support code to check
|
||||
memory allocations and array/pointer bounds. @option{-g} is implied. Note
|
||||
that the generated code is slower and bigger in this case.
|
||||
The bound checking code is not included in shared libraries. The main executable should always be compiled with the @option{-b}.
|
||||
|
||||
There are five environment variables that can be used:
|
||||
@table @option
|
||||
@item TCC_BOUNDS_WARN_POINTER_ADD
|
||||
Print warning when pointer add creates an illegal pointer.
|
||||
@item TCC_BOUNDS_PRINT_CALLS
|
||||
Print bound checking calls. Can be used for debugging.
|
||||
@item TCC_BOUNDS_PRINT_HEAP
|
||||
Print heap objects that are not freed at exit of program.
|
||||
@item TCC_BOUNDS_PRINT_STATISTIC
|
||||
Print statistic information at exit of program.
|
||||
@item TCC_BOUNDS_NEVER_FATAL
|
||||
Try to continue in case of a bound checking error.
|
||||
@end table
|
||||
|
||||
Note: @option{-b} is only available on i386 (linux and windows), x86_64 (linux and windows), arm, arm64 and riscv64 for the moment.
|
||||
Generate additional support code to check memory allocations and array/pointer
|
||||
bounds (@pxref{Bounds}). @option{-g} is implied.
|
||||
|
||||
@item -bt[N]
|
||||
Display N callers in stack traces. This is useful with @option{-g} or @option{-b}.
|
||||
@@ -686,8 +668,6 @@ are supported.
|
||||
@item Binary digits can be entered (@code{0b101} instead of
|
||||
@code{5}).
|
||||
|
||||
@item @code{__BOUNDS_CHECKING_ON} is defined if bound checking is activated.
|
||||
|
||||
@end itemize
|
||||
|
||||
@node asm
|
||||
@@ -881,16 +861,7 @@ GROUP ( /lib/libc.so.6 /usr/lib/libc_nonshared.a )
|
||||
@cindex bound checks
|
||||
@cindex memory checks
|
||||
|
||||
This feature is activated with the @option{-b} (@pxref{Invoke}).
|
||||
|
||||
Note that pointer size is @emph{unchanged} and that code generated
|
||||
with bound checks is @emph{fully compatible} with unchecked
|
||||
code. When a pointer comes from unchecked code, it is assumed to be
|
||||
valid. Even very obscure C code with casts should work correctly.
|
||||
|
||||
For more information about the ideas behind this method, see
|
||||
@url{http://www.doc.ic.ac.uk/~phjk/BoundsChecking.html}.
|
||||
|
||||
This feature is activated with the @option{-b} option (@pxref{Invoke}).
|
||||
Here are some examples of caught errors:
|
||||
|
||||
@table @asis
|
||||
@@ -946,41 +917,58 @@ Here are some examples of caught errors:
|
||||
free(tab);
|
||||
@}
|
||||
@end example
|
||||
|
||||
@end table
|
||||
|
||||
Signal handlers are not compatible with bounds checking. The code
|
||||
below can be used to protect signal handlers.
|
||||
The @code{__attribute__((bound_no_checking))} will prevent all bound checking
|
||||
code generation. If a signal handler calls another function this
|
||||
function must also use @code{__attribute__((bound_no_checking))}.
|
||||
TCC defines @code{__BOUNDS_CHECKING_ON} if activated.
|
||||
|
||||
The fork() function call in a multi threaded application is also a problem.
|
||||
To solve this all bounds checking can be disabled by calling
|
||||
@code{__bound_checking(1)}. The call to @code{__bound_checking(1)} will disable bounds
|
||||
checking in the whole application.
|
||||
There are five environment variables that can be used to control the behavior:
|
||||
@itemize
|
||||
@item TCC_BOUNDS_WARN_POINTER_ADD
|
||||
- Print warning when pointer add creates an illegal pointer.
|
||||
@item TCC_BOUNDS_PRINT_CALLS
|
||||
- Print bound checking calls. Can be used for debugging.
|
||||
@item TCC_BOUNDS_PRINT_HEAP
|
||||
- Print heap objects that are not freed at exit of program.
|
||||
@item TCC_BOUNDS_PRINT_STATISTIC
|
||||
- Print statistic information at exit of program.
|
||||
@item TCC_BOUNDS_NEVER_FATAL
|
||||
- Try to continue in case of a bound checking error.
|
||||
@end itemize
|
||||
|
||||
The @code{BOUNDS_CHECKING_OFF} and @code{BOUNDS_CHECKING_ON} can also be used to
|
||||
disable bounds checking for some code. This is not recommended.
|
||||
It is better to fix the code.
|
||||
Also, a function @code{__bounds_checking(x)} can be used to turn off/on bounds
|
||||
checking from usercode (see below).
|
||||
|
||||
Notes:
|
||||
@itemize
|
||||
@item Only available on i386 (linux and windows), x86_64 (linux and windows),
|
||||
arm, arm64 and riscv64 for the moment.
|
||||
@item The generated code is slower and bigger.
|
||||
@item The bound checking code is not included in shared libraries. The main
|
||||
executable should always be compiled with the @option{-b}.
|
||||
@item Pointer size is @emph{unchanged} and code generated with bound checks is
|
||||
@emph{fully compatible} with unchecked code. When a pointer comes from
|
||||
unchecked code, it is assumed to be valid. Even very obscure C code with
|
||||
casts should work correctly.
|
||||
@item Signal handlers are not compatible with bounds checking. The fork()
|
||||
function call in a multi threaded application is also a problem.
|
||||
The code below can be used to solve this.
|
||||
@end itemize
|
||||
|
||||
@example
|
||||
|
||||
#if defined(__TINYC__) && __BOUNDS_CHECKING_ON
|
||||
#undef __attribute__
|
||||
extern void __bound_checking (int no_check);
|
||||
#define BOUNDS_CHECKING_OFF __bound_checking(1)
|
||||
#define BOUNDS_CHECKING_ON __bound_checking(-1)
|
||||
#define BOUNDS_NO_CHECKING __attribute__((bound_no_checking))
|
||||
#ifdef __BOUNDS_CHECKING_ON
|
||||
extern void __bounds_checking (int x);
|
||||
# define BOUNDS_CHECKING_OFF __bounds_checking(1)
|
||||
# define BOUNDS_CHECKING_ON __bounds_checking(-1)
|
||||
#else
|
||||
#define BOUNDS_CHECKING_OFF
|
||||
#define BOUNDS_CHECKING_ON
|
||||
#define BOUNDS_NO_CHECKING
|
||||
# define BOUNDS_CHECKING_OFF
|
||||
# define BOUNDS_CHECKING_ON
|
||||
#endif
|
||||
|
||||
void signal_handler(int sig, void *info, void *ucontext) BOUNDS_NO_CHECKING
|
||||
void signal_handler(int sig, void *info, void *ucontext)
|
||||
@{
|
||||
BOUNDS_CHECKING_OFF;
|
||||
... signal handler code without generated bounds checking code.
|
||||
BOUNDS_CHECKING_ON;
|
||||
@}
|
||||
|
||||
void run(const char *cmd)
|
||||
@@ -999,9 +987,11 @@ void run(const char *cmd)
|
||||
break;
|
||||
@}
|
||||
@}
|
||||
|
||||
@end example
|
||||
|
||||
For more information about the ideas behind this method, see
|
||||
@url{http://www.doc.ic.ac.uk/~phjk/BoundsChecking.html}.
|
||||
|
||||
@node Libtcc
|
||||
@chapter The @code{libtcc} library
|
||||
|
||||
|
||||
Reference in New Issue
Block a user