[ae6f1ec] | 1 | #include <stdio.h> |
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| 2 | #include "except.h" |
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| 3 | |
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[6b72040] | 4 | // Requires -fexceptions to work. |
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| 5 | |
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[ae6f1ec] | 6 | #define EXCEPTION 2 |
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| 7 | |
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| 8 | struct type_raii_t { |
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| 9 | char * msg; |
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| 10 | }; |
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| 11 | |
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| 12 | //Dtor function to test clean up routines |
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| 13 | void dtor( struct type_raii_t * this ) { |
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| 14 | printf("%s\n", this->msg); |
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| 15 | } |
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| 16 | |
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| 17 | //Type macro use to make scope unwinding easier to see. |
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| 18 | #define raii_t __attribute__(( cleanup(dtor) )) struct type_raii_t |
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| 19 | |
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| 20 | //Leaf functions that raises exception |
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| 21 | void bar() { |
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| 22 | raii_t a = { "Bar dtor" }; |
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| 23 | |
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| 24 | throw( EXCEPTION ); |
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| 25 | } |
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| 26 | |
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| 27 | //Matcher function which will check if the exception was correctly caught |
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| 28 | extern int this_exception; |
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| 29 | _Unwind_Reason_Code foo_try_match() { |
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[6b72040] | 30 | printf(" (foo_try_match called)"); |
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| 31 | return this_exception == EXCEPTION ? _URC_HANDLER_FOUND : _URC_CONTINUE_UNWIND; |
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[ae6f1ec] | 32 | } |
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| 33 | |
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| 34 | //Try statements are hoisted out see comments for details |
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| 35 | //With this could probably be unique and simply linked from |
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| 36 | //libcfa but there is one problem left, see the exception table |
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| 37 | //for details |
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[4a58895] | 38 | __attribute__((noinline)) |
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[6b72040] | 39 | void try( void (*try_block)(), void (*catch_block)(), |
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| 40 | _Unwind_Reason_Code (*match_block)() ) |
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[ae6f1ec] | 41 | { |
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[6b72040] | 42 | volatile int xy = 0; |
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| 43 | printf("%p %p %p %p\n", &try_block, &catch_block, &match_block, &xy); |
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| 44 | |
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[ae6f1ec] | 45 | //Setup statments |
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| 46 | //These 2 statments won't actually result in any code, |
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| 47 | //they only setup global tables. |
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| 48 | //However, they clobber gcc cancellation support from gcc. |
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| 49 | //We can replace the personality routine but replacing the exception |
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| 50 | //table gcc generates is not really doable, it generates labels based |
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| 51 | //on how the assembly works. |
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| 52 | //Setup the personality routine |
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| 53 | asm volatile (".cfi_personality 0x3,__gcfa_personality_v0"); |
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| 54 | //Setup the exception table |
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| 55 | asm volatile (".cfi_lsda 0x3, .LLSDACFA2"); |
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| 56 | |
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| 57 | //Label which defines the start of the area for which the handler is setup |
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| 58 | asm volatile (".TRYSTART:"); |
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| 59 | |
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| 60 | //The actual statements of the try blocks |
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| 61 | try_block(); |
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| 62 | |
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| 63 | //asm statement to prevent deadcode removal |
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| 64 | asm volatile goto ("" : : : : CATCH ); |
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| 65 | |
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| 66 | //Normal return |
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| 67 | return; |
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| 68 | |
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| 69 | //Exceptionnal path |
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| 70 | CATCH : __attribute__(( unused )); |
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| 71 | //Label which defines the end of the area for which the handler is setup |
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| 72 | asm volatile (".TRYEND:"); |
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| 73 | //Label which defines the start of the exception landing pad |
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| 74 | //basically what will be called when the exception is caught |
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| 75 | //Note, if multiple handlers are given, the multiplexing should be done |
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| 76 | //by the generated code, not the exception runtime |
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| 77 | asm volatile (".CATCH:"); |
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| 78 | |
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| 79 | //Exception handler |
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| 80 | catch_block(); |
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| 81 | } |
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| 82 | |
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| 83 | //Exception table data we need to generate |
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| 84 | //While this is almost generic, the custom data refers to |
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| 85 | //foo_try_match try match, which is no way generic |
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| 86 | //Some more works need to be done if we want to have a single |
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| 87 | //call to the try routine |
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| 88 | asm ( |
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| 89 | //HEADER |
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| 90 | ".LFECFA1:\n" |
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| 91 | " .globl __gcfa_personality_v0\n" |
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| 92 | " .section .gcc_except_table,\"a\",@progbits\n" |
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| 93 | ".LLSDACFA2:\n" //TABLE header |
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| 94 | " .byte 0xff\n" |
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| 95 | " .byte 0xff\n" |
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| 96 | " .byte 0x1\n" |
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| 97 | " .uleb128 .LLSDACSECFA2-.LLSDACSBCFA2\n" //BODY length |
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| 98 | //Body uses language specific data and therefore could be modified arbitrarily |
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| 99 | ".LLSDACSBCFA2:\n" //BODY start |
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| 100 | " .uleb128 .TRYSTART-try\n" //Handled area start (relative to start of function) |
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| 101 | " .uleb128 .TRYEND-.TRYSTART\n" //Handled area length |
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| 102 | " .uleb128 .CATCH-try\n" //Hanlder landing pad adress (relative to start of function) |
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| 103 | " .uleb128 1\n" //Action code, gcc seems to use always 0 |
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| 104 | ".LLSDACSECFA2:\n" //BODY end |
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| 105 | " .text\n" //TABLE footer |
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| 106 | " .size try, .-try\n" |
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| 107 | " .ident \"GCC: (Ubuntu 6.2.0-3ubuntu11~16.04) 6.2.0 20160901\"\n" |
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| 108 | " .section .note.GNU-stack,\"x\",@progbits\n" |
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| 109 | ); |
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| 110 | |
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| 111 | void foo() { |
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| 112 | raii_t a = { "Foo dtor" }; |
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| 113 | |
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| 114 | //Since try will clobber the gcc exception table assembly, |
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| 115 | //We need to nest this to have gcc regenerate the data |
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| 116 | void foo_try_block() { |
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| 117 | raii_t b = { "Foo try dtor" }; |
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| 118 | |
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| 119 | bar(); |
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| 120 | |
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| 121 | printf("Called bar successfully\n"); |
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| 122 | } |
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| 123 | |
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| 124 | void foo_catch_block() { |
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| 125 | printf("Exception caught\n"); |
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| 126 | } |
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| 127 | |
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| 128 | //Actual call to the try block |
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[6b72040] | 129 | try( foo_try_block, foo_catch_block, foo_try_match ); |
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[ae6f1ec] | 130 | |
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| 131 | printf( "Foo exited normally\n" ); |
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| 132 | } |
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| 133 | |
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[6b72040] | 134 | // Not in main.cfa |
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| 135 | void fy() { |
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| 136 | // Currently not destroyed if the exception is caught in fee. |
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| 137 | raii_t a = { "Fy dtor" }; |
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| 138 | |
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| 139 | void fy_try_block() { |
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| 140 | raii_t b = { "Fy try dtor" }; |
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| 141 | |
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| 142 | throw( 3 ); |
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| 143 | } |
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| 144 | |
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| 145 | void fy_catch_block() { |
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| 146 | printf("Fy caught exception\n"); |
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| 147 | } |
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| 148 | |
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| 149 | _Unwind_Reason_Code fy_match_block() { |
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| 150 | return this_exception == 2 ? _URC_HANDLER_FOUND : _URC_CONTINUE_UNWIND; |
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| 151 | } |
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| 152 | |
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| 153 | try(fy_try_block, fy_catch_block, fy_match_block); |
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| 154 | |
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| 155 | printf( "Fy exited normally\n" ); |
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| 156 | } |
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| 157 | |
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| 158 | void fee() { |
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| 159 | raii_t a = { "Fee dtor" }; |
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| 160 | |
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| 161 | void fee_try_block() { |
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| 162 | raii_t b = { "Fee try dtor" }; |
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| 163 | |
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| 164 | fy(); |
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| 165 | |
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| 166 | printf("fy returned\n"); |
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| 167 | } |
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| 168 | |
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| 169 | void fee_catch_block() { |
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| 170 | printf("Fee caught exception\n"); |
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| 171 | } |
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| 172 | |
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| 173 | _Unwind_Reason_Code fee_match_block() { |
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| 174 | return this_exception == 3 ? _URC_HANDLER_FOUND : _URC_CONTINUE_UNWIND; |
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| 175 | } |
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| 176 | |
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| 177 | try(fee_try_block, fee_catch_block, fee_match_block); |
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| 178 | |
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| 179 | printf( "Fee exited normally\n" ); |
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| 180 | } |
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| 181 | // End not in main.cfa |
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| 182 | |
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[ae6f1ec] | 183 | int main() { |
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| 184 | raii_t a = { "Main dtor" }; |
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| 185 | |
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[6b72040] | 186 | //for (unsigned int i = 0 ; i < 100000000 ; ++i) |
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| 187 | foo(); |
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| 188 | fee(); |
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[ae6f1ec] | 189 | |
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| 190 | printf("End of program reached\n"); |
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[88e0080] | 191 | } |
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