README (7430B)
1 Compiling 2 ========= 3 4 SCC is a portable toolchain that can be compiled on any UNIX system 5 out of the box. It supports several configuration options that 6 can be passed to the command line: 7 8 - PREFIX: Prefix of the path where scc toolchain is going 9 to be installed. /usr/local by default. 10 11 - LIBPREFIX: Prefix of the path where scc searchs for 12 headers and libraries when scc is executed. $PREFIX 13 by default. 14 15 - DESTDIR: Temporary directory prepend to PREFIX used in the 16 install path. It is mainly intended to help package maintainers 17 to install in a specific directory used as base for the package 18 generation. 19 20 - CROSS_COMPILE: 21 Specify a prefix name for the tools called by the Makefile. 22 23 - HOST: 24 Specify the host system to be used. Possible supported 25 values are: 26 27 - unix (by default) 28 - bsd 29 - plan9 30 31 - CONF: Specify which version of libc to build. 32 Once the build process completes only the target specified in 33 CONF will be built. Supported values are: 34 35 - amd64-linux (default) 36 - amd64-darwin 37 - amd64-openbsd 38 - arm64-linux 39 - amd64-dragonfly 40 - amd64-freebsd 41 - amd64-netbsd 42 - arm32-linux 43 - i386-linux 44 45 Not all the configurations have the same level of support in 46 the libc and in some cases the support is minimal. 47 48 - TOOL: Specify the toolchain type to be used. Possible 49 supported values are: 50 51 - unix (by default) 52 - gnu 53 - gnu-darwin 54 - clang 55 - pcc 56 - plan9 57 58 Beware that the default target selects the appropiate value for HOST, 59 CONF and TOOL. In case of being needed, TOOL can be still overloaded 60 in the command line. 61 62 The main targets of the Makefile are: 63 64 - all: 65 Compile the toolchain and the libc. It automatically 66 determines what is the best value for HOST. It sets the 67 value of CONF for the toolchain that is used by the 68 toolchain as the default target. It also compiles the libc 69 for all the available configurations based in the host 70 architecture. 71 72 - config 73 Generate headers supposed to be customized by the user. 74 75 - toolchain 76 Compile the toolchain with the default configuration 77 specified in CONF. Beware that this target is executed without 78 the automatic detection of the host parameters. It makes 79 easier to cross compile. 80 81 - libc: 82 Compile the libc for the target specified in CONF. Beware 83 that this target is executed without the automatic detection 84 of the host parameters. It makes easier to cross compile. 85 86 - install: 87 Installs scc in PREFIX. 88 89 - clean: 90 Remove all the generated files except the one supposed to be edited 91 by the user. 92 93 - distclean 94 Remove all the generated files. 95 96 Toolchain configuration 97 ======================= 98 At this moment scc is still using some external tools to generate 99 the final binaries. The toolchain execution is configured in the 100 file `include/scc/scc/sys.h` and it included basically 5 elements: 101 102 - LDBIN: macro with the name of the linker binary. 103 104 - ASBIN: macro with the name of the assembler binary. 105 106 - sysincludes: It is a list of diretories used to locate 107 the system headers 108 109 - ldcmd: It describes how the linker command line is built. 110 111 - ascmd: It describes how the assembler command line is built. 112 113 The definition of sysincludes, ldcmd and ascmd can include wildcards 114 represented by % followed by a single letter: 115 116 - %c: It expands to the full list of input object files of the linker 117 - %a: It expands to the architecture name 118 - %s: It expands to the system name 119 - %p: It expands to the library prefix 120 - %b: It expands too the ABI name 121 - %o: It expands to the output file of the current tool 122 123 Scc includes 3 configuration templates that can be used as base for the 124 configuration of the toolchain: 125 126 - scc: It uses GNU assembler and linker with the scc libc. 127 - scc_clang: It uses clang assembler and linker with the scc libc. 128 - musl: It uses GNU assembler and linker with the musl libc. 129 130 The file `include/scc/scc/sys.h` is automatically created from the scc 131 toolchain configuration with the default make target. The target config 132 can be used to only create the file based on the value of the variable 133 `LIBPROFILE` allowing the user to customize that file as needed. It is 134 important to highlight that the file is not removed by `make clean` 135 because it can contain local user modifications. You should use 136 `make distclean` to remove it. 137 138 139 Musl libc support 140 ================= 141 The scc libc is a C99 library and cannot be used to compile POSIX compliant 142 programs. Scc includes a template that can be used to use a musl libc 143 compiled by gcc: 144 145 $ make LIBPROFILE=musl config 146 147 It will generate the files sys.h configured to be used with a musl 148 libc. Beware that it is likely that those files have to be customized to 149 fit your system because the macro GCCLIBPATH used by the musl template 150 depends heavily of the toolchain used to compile musl. As the musl libc 151 is likely installed in a different prefix the scc compilation must be 152 modified to: 153 154 $ make LIBPREFIX=/usr/local/musl # point to the prefix used by your musl 155 156 If the helper scc shell script is used instead of scc-cc then the 157 environment variable SCCLIBPREFIX must be set: 158 159 $ SCCLIBPREFIX=/usr/local/musl scc hello.c 160 161 Deviations from standard C 162 =========================== 163 This compiler aims to be fully compatible with the C99 standard, but 164 it has some differences at this moment: 165 166 - Type qualifiers are accepted but partially ignored. 167 -------------------------------------------------- 168 169 The semantic behind them is not fully implemented, specially in the 170 case of volatile. Be aware that some programs can miswork for this 171 reason. 172 173 - Function type names 174 ------------------- 175 176 C99 allows you to define type names of function types and write something 177 like: 178 179 int f(int (int)); 180 181 Accepting function types in type names (or abstract declarators) makes the 182 grammar ambiguous because it is impossible to differentiate between: 183 184 (int (f)) -> function returning int with one parameter of type f 185 (int (f)) -> integer variable f 186 187 If you don't believe me try this code: 188 189 int 190 f(int g()) 191 { 192 return g(); 193 } 194 195 Function type names seem unnecesary , because they are used as 196 an alias of the function pointer types, but it is weird that something 197 like sizeof(int (int)) is not allowed (because here it should be 198 understood as the size of a function), but f(int (int)) is allowed 199 because it is understood as a parameter of function pointer type. 200 201 - Definition of variables with incomplete type 202 --------------------------------------------- 203 204 C89 allows the definition of variables with incomplete type that 205 have external linkage and file scope. The type of the variable is the 206 composition of all the definitions found in the file. The exact rules 207 are a bit complex (ANSI 3.7.2, or ISO C99 6.2.5p22) so SCC ignores them 208 at this moment by simply not allowing any definition of variables with 209 incomplete type. 210 211 If you don't believe me try this code: 212 213 struct foo x; 214 215 struct foo { 216 int i; 217 }; 218 219 - Variadic function alike macros 220 ------------------------------ 221 222 The standard (C99 6.10.3 c 4) forces passing more parameters than 223 the number of parameters present in the variadic argument list 224 (excluding ...). SCC accepts a parameter list with the same number 225 of arguments. 226 227 #define P(a, ...) a 228 229 P(1) 230 231 C99 libc 232 ======== 233 234 The C99 libc only supports the C locale using UTF-8 for multibyte 235 sequences. It also assumes that the wide character set includes 236 ASCII as a subset.