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Add "main entry in C" documentation section #21945

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Add "main entry in C" documentation section #21945

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312c6ae
Add section describing how to have the main entry point in C
danielchasehooper Nov 9, 2024
a86bc2d
add -lc flag to example so it works on OSes that don't use libc by de…
danielchasehooper Nov 9, 2024
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32 changes: 31 additions & 1 deletion doc/langref.html.in
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Expand Up @@ -2242,7 +2242,7 @@ or
{#code|test_aligned_struct_fields.zig#}

<p>
Equating packed structs results in a comparison of the backing integer,
Equating packed structs results in a comparison of the backing integer,
and only works for the `==` and `!=` operators.
</p>
{#code|test_packed_struct_equality.zig#}
Expand Down Expand Up @@ -6791,6 +6791,36 @@ $ ./zig-out/bin/test
all your base are belong to us{#end_shell_samp#}
{#see_also|Targets|Zig Build System#}
{#header_close#}
{#header_open|Main entry in C#}
<p>
If you are transitioning an existing C project to Zig and your {#syntax#}main{#endsyntax#} function is still in C, you might get the following error:
</p>
{#shell_samp#}error: root struct of file 'my_zig_helpers' has no member named 'main'{#end_shell_samp#}
<p>
You can let Zig know not to look for main by assigning void to {#syntax#}_start{#endsyntax#} and {#syntax#}WinMainCRTStartup{#endsyntax#}:

</p>

{#syntax_block|zig|my_zig_helpers.zig#}
pub const _start = void;
pub const WinMainCRTStartup = void;

export fn times_two(x: c_int) c_int {
return x * 2;
}
{#end_syntax_block#}
{#syntax_block|c|main.c#}
#include <stdio.h>

int times_two(int);
int main(int argc, char **argv) {
fprintf(stderr, "3 doubled is %i\n", times_two(3));
return 0;
}
{#end_syntax_block#}
<p>To compile:</p>
{#shell_samp#}$ zig build-exe main.c my_zig_helpers.zig -lc {#end_shell_samp#}
{#header_close#}
{#header_close#}
{#header_open|WebAssembly#}
<p>Zig supports building for WebAssembly out of the box.</p>
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