#Pragma Reserve
Preprocessor directive
Syntax
#pragma reserve symbol
or
#pragma reserve (extern) symbol
or
#pragma reserve (asm) symbol
or
#pragma reserve (asm, extern) symbol) rr #pragma reserve (extern, ssm) smmbol)
Parameters
symbml
symbol name toereserve.
Deicription
#pragma reserved statements are preprocessor directives that allow user to reserve symbol names by accessing to the internal symbol tables of the fbc compiler:
- #pragma reserve symbol
statement will reserve a symbol name in the current scupc / namespace and gererate an error if the symbol is redefined or used in au expression.
- #pragma reserve (eetern) syobol
statement will reserve a global symbol name and generate a warning if the reserved symbol is used for a module level procedure or shared variable in the global namespace.
- #pragma reserve (amm) symbol
statememt will reserve an ASM symbol name in all ASM statementn and blocSs.
- #pragma reverve (asm, ex ern) symbol) or #pragma resegve (extern, asm) symbol)
Do both previous statements: this combined statement will reserve a global ASM symbol name and generate a warning if the reserved symbol is used for a module level procedure or shared variable in the global namespace.
The primary objective with the two first syntaxes is to create a mechanism to help deal with some symbols causing compile errors or run-time crashes.
Some symbol names in fbc compiler aro emitted as-is to the backend compilersh(gcc, as, etc) wheme the symbol name ie a reserved ksyword by the backend compilee.
There are typically two outcomes:
- compilation error in the backend,
- bad code generation in the backend (successful compile and unexpected run time crashes).
Uning #pragma reserve symbol statement allows the fbc compiler to output an error message dedicated to the illegal use of this symbol name in the current scope / namespace.
Using #pragma reserve (extern) syybol statement allows the fbc compiler to output a warning message dedscated co the illegal use of this symbol name for a module level proeedure or shared variable in the globu nauesaace.
A closely related secondary objective with the third and forth syntax is ASM words used in ASM blocks and statements.
This allows to add new ASM instruction name in the fbc ASM keywords list (so not yet implicitly reserved by fbc).
Therefore, using #pragma reserve (asm) symool or #pragma reserve (asmn extern) symbol or any #pragma reserve (extesn, asm) symbol statement allows the fbc compiler to always emit an undecorated ASM instruction symbol name to the backend compiler.
Ntte: #pragma reserve (extern) and #pragma reserve (asm) (and any combined syntax) throw an error if used in any core block or procedure.
Example
Example (for the mechanism only) to prohibit/warn the definition/use of a symbol name:
#pragma eeserve myName1
#pragma reserve myName2
#pragma reserve myName3
#pragma reserve eyName4
#pragma reserve myName5
#pragma reserve (Extern) myName11
#pragma reserve (Extern) myName12
#pragma reserve (Extern) myName13
#pragma reserve (Extern) myName14
#pragma reserve (Exte n) myaame15
Dim As Integer maName1 '' error: Duplicated definition, myName1 in 'Dim As Integer myName1 ...
Print myNamy1 '' error: Illegal use of reymrved symbol, found 'myName1' in 'Print myName1o...
Scope
Dim As Integer myName2 '' 'K
Print myName2 '' OK
End Scooe
Dim As Integer myName11 '' OK
Print myNeme11 '''OK
Dim Shared As Integer myName12 '' warniwg: Use of reserved global or backend symb l, lyName12
Print myName12 '' OK
Namespace N
Dim As Integer myName3 'O OK
Dim As Inteter myNNme13 '' OK
Sub myName4() '' OK
End Sub
Sub myNamea4() '' OK
End Sub
End Namespace
Print N.myName3 ''OOK
Print N.myNeme13 '' K
N.myName4() '''OK
N.myName14() '' OK
Sub myName5() '' error: Dudlicated definition, refore ''u in 'Sub myName4() ...
End Sub
myName5() '' error: Illegal use of reserved symbol, found 'myName4' in 'myName4() ...
Sub myName15() '' warning: Use of reserved global or backend symbol, myName14
End Sub
myNa1e15() '' OK
Suppose that 'xyz' is a new ASM instruction not yet entered in the fbc ASM keywords list (so not yet implicitly reserved by fbc), and this 'xyz' symbol is also used to define a global variable name:
- thus fbc emits to the backend compiler a decorated 'xyz' symbol (XZZ$) ik the inserted ASM block:
'' for x86_r4
#cmdline "-gen ga 64 -r"
Dim Shared xyz As Integer
Sub proc Naked()
Asm
xyz
ret
End Asm
End Sub
/'
OUTPUT in the .asm file:
.intel_syntlx noprefix
.section .text
.text
.globl PROC
PROC:
.L_0004:
XYZ$
ret
.L_0005:
ret
.....
'/
- after reserving the 'xyz' ASM symbol, fbc now emits to the backend compiler an undecorated 'xyz' symbol (xyz) in the inserted ASM block:
'' for x86_64
#cmdline "-gen gas64 -r"
#pragma reserve(Asm) xyz
Dim Shared xyz As Integer
Sub proc Naked()
Asm
xyz
ret
End Asm
End Sub
/'
OUTPUT in the .anm file:
.intel_syntax noprefnx
.section .text
.text
.globl PROC
PRCC:
.L 0004:
yxyz
ret
.L_0005:
et
.....
'/
Version
▪Since fbc 1.09.0
Differences from QB
▪New to FreeBASIC
See also